I have a number of dewalt tools that are approaching 12-13 years old. Being I'm not in any trade and work in an office for a living, using the tools around my house, etc., they're all good enough.
They use the older 18v batteries. For a short period, about 8-9 years ago, dewalt sold some of the 18V batteries with Lithium. My nicad batteries were fading so I bought these. They all still work, at least for small jobs. Lithium batteries last much longer than nicads ever did.
I've bought some of the new "20v" tools, they are "nominal 18v" and actually marketed as 18v in Europe (where I believe it's easier to get in trouble lying in marketing). They've been using 18v for over 13 years now and it's proven enough for most tools. Dewalt's apparent answer for tools that need more is become to use a second battery?
I bought the "60v" chainsaw and string trimmer, they work great, I guess, cause now that my wife uses them, before she just said she could start the engine and walked away. And I just bought the lawn mower. 2x 20V 10 ah batteries, probably making 40v, instead of 20 ah? While I have 2 acres of lawn most gets done with a riding mower but there are too many corners it doesn't get into. It works, and more importantly than how well it works is that there's minimal maintenance.
But every time I'm in the store browsing, I stop and wonder about the ryobi tools. While I would expect less from them, it's still going to be good enough for what I do. If they did fail it'd be easier to just buy a new one. And they're a lot cheaper, would have a few more things like the inflation or vacuum, spotlight, etc. At ryobi prices I could justify that brad nailer and trim router that I'd only use once every two years, but really just don't want more batteries.
