I’ve been Ryobi 18v for about 20 years now (I also use Milwaukee‘s 12v system). I went to it bc of the long term battery compatibility and range of products (auto, lawn, and woodworking) at the time that I was making a choice. For me, the batteries begin to show decreased capacity and a become not useful around the 10-12 year mark. I think I currently have 7-ish batteries that I rotate through.
Before that it was a Porter Cable 18v and a craftsman 12v, and so I was a little sour when those companies that ended their respective battery platforms.