Replying out of order, and then I'm done with this discussion because I can't add anything more of value.
How much service and repair work have you performed on your 2013?
I've done very little repair work on the 200 as it's been pretty solid. Lots of maintenance and mods. Some of them I do, some of them I've paid a shop to do. For instance I paid a shop to do my gears and lockers because it requires precision and patience (particularly the front diff), but I did the lift because that's mainly just brute force. I paid a shop to install the front bumper and winch because I only had a few days to get it installed before a long trip, but I did the rear swingout bumper myself over the course of a week. I have a shop I trust who does fluid swaps for me because until last year I didn't have a place I could do them myself, and now I still do because while I like to get under the truck to inspect I also see the value in having a second set of eyes look over my truck twice a year.. and quite frankly it's worth me paying for the labor to avoid the mess and hassle of working on my back under the truck in the cold. I follow a pretty aggressive fluid/maintenance schedule which is pretty close to what is in the SOC, and I pretty much shun the unnecessary crap dealers often try to push, though in fairness my local dealer has never tried to offer any of those services to me. (I can change my own blinker fluid, TYVM!)
Yes, any transmission tech/shop owner will tell you that servicing the transmission regularly (50-60k miles) will benefit the transmission by replenishing the additives.
3. It might not be recent theory or information, but I've learned lately that there's some science to NOT doing a full-on fluid flush after 100 or 130k miles if you haven't been doing that prior at some interval. The reason being is the fluid has a healthy amount of friction material from the clutch plates that actually assist the clutch plates now with 'grip'. If you have the 250k mile vehicle, never having serviced the transmission and then decide to completely replace the fluid, you're washing away literally most of the grip the clutch plates had.
It seems the better service theory is to start early with servicing the transmission, a pan drop, filter replacement and refill, as this helps prevent the friction material from wearing off the clutch plates.
I do what I feel is right based on listening to people that have in-depth experience and have studied issues. I'm not here to argue, just the opposite, I'd rather share what I feel are beneficial experiences.
There are 2 sides to #3. The friction material causing the transmission to work with old fluid but not with new fluid is the same friction material that's circulating through the transmission and also slowly wearing down the internal components. I am fully of the opinion that if you maintain your transmission with regular fluid exchanges from the start that the small amounts of friction material you lose are more than offset by keeping fresh fluid with proper additives in the system which largely prevents the clutch plates from wearing rapidly to begin with. I mean, when they build a new transmission it's not like Toyota is tossing a handful of sand into the system to make sure the clutch packs have sufficient friction, so fresh fluid in a non-worn transmission must have the correct amount of friction to function properly, right?
However as I've said if you have a vehicle with ~200k and it's never had the transmission fluid flushed, it's perfectly reasonable to either do a pan-only swap or just leave it alone at that point, depending on fluid condition and mileage. I don't dispute that once the clutch packs are worn and don't engage like they should that you should be careful about upsetting the existing system (which includes fluid). Again I'll point out at that point you are living on borrowed time anyway.
In the end you can do whatever maintenance you'd like however you'd like it. Honestly these transmissions will go 300k before needing a rebuild even if you don't do anything to them, provided they haven't seen absurd levels of abuse.
1. Nobody said it is "Lifetime" fluid. It's nowhere in the owner's manual or service manual. Toyota side-steps any recommendation to service the transmission outside of "heavy/frequent towing". Toyota and it's dealers also tell every single customer they are 'good to go' for 10k mile oil change intervals, without ever interrogating the customer about their driving habits. The owner's manual states otherwise.
Re: #1 - Rather than dispute the meaning of the word "Lifetime", I'm simply going to provide facts
My 2013 manual says for normal driving to inspect at 60k and then at 30k intervals thereafter. No where in the first 120k does is say to replace during normal usage. No where does the manual say "replace at 100k under normal driving conditions" (or "if you go easy on it"). The open point of discussion should only be what to do if the fluid inspection reveals it's burnt or contains water infiltration - do you swap just the pan or do you exchange all of it?
Also under Special Operating Conditions is says when towing or heavy vehicle loading to "Replace automatic transmission fluid". No where does it say "replace some of your A/T fluid". Given the maintenance schedule, it seems completely reasonable to me to replace all the fluid if you fall under the SOC, or if normal duty A/T fluid inspection reveals the fluid is compromised.
2. I believe the transmission fluid capacity is about 12 quarts? I'm assuming you believe that also, since you most likely feel a pan drop/filter change and refill equates to about 3-4 quarts and you're calling that 1/4 of the fluid? Well, in my experiences of dropping the pan on both my LX and Tundra, replacing the filter and refilling, I am using over 5.5 quarts of transmission fluid to refill the pan and only getting about 6-8 oz out of the check plug when the fluid temp reaches 116°F. I'd call that more than 1/4 of the fluid being replaced.
As to #2 - Officially the system holds 12.6 quarts. The dealer by me charges for 12 quarts when doing a fluid exchange. Maybe I'm getting 0.6 free quarts, or maybe they're not quite swapping all the fluid.
Also officially the FSM says just doing a pan drain/fill should be 2.2 quarts. I'm not going to dispute that you may end up draining more off as most people have found they end up draining somewhere in the neighborhood of 3-4 quarts out as there are several factors which will affect the precise amount of fluid drained including fluid temperature (warm fluid will drain better and also has more volume than cold fluid, if you've added a lift and changed the rake of your vehicle the pan may no longer be perfectly level, etc).
BTW the FSM has instructions on how to drain the system and fill it when you've replaced the pan, valve body, or TC, all of which involve filling the pan, shifting through the gears for 30 seconds, then shutting off and adding more fluid if it's not coming out the overflow plug. I cannot find any maintenance procedure in the Toyota FSM which says to only drain and refill the pan when doing the above maintenance.
