50K on my 19 as well. When I get to ~90K it will be decision time. If I keep it will do waterside replacement, radiator, water pump, etc. Valley plate leak preventive maintenance not sure about but after 20 years of working in the engine rooms of ships I'm used to tearing apart perfectly good operating machinery to do preventive maintenance. Except I am too old for that crap now and have to pay someone else to do it. At that time may be looking at a LX600 if I'm still around and not farting dust.
Tranny doing drain and fills plus cooler so not really concerned about the life of the tranny I think the failure rate is pretty low especially if you keep the ATF cool and clean.
I tow ~2,500 pounds around 20 times a year usually long distances. I monitor tranny temps with OBDLink Fusion for all trips of any distance. As long as I am moving even going up the steep Mississippi River bluffs temps don't really get that much higher than normal. It is the stop and go where it really climbs. This summer got in a long stop and go line on the highway for road construction and it broke 230° in both the pan and TC. Why I ordered a cooler. Plus just normal driving I feel it runs a bit higher than I'd like.