FWIW: I have torches, MP3 players, dictaphones, powerpacks and satnavs well over 10yrs old, and I have never bought a replacement battery. They all have Li-Ion batteries as far as I know. All my RC stuff runs on Li-Poly batteries, and again, some of them are over 15yrs old, and all still work well. I never fast charge any of them. The Ni-Cads however, which I use for same of my RC controllers was a different story, to the point where I have converted some Li-Ion packs to do the job.
These battery packs will have fewer cells than traction batteries, a common problem is one faulty cell limiting the batteries charging, and discharging ability, quite often this can be resolved by continuing to charge beyond full to force the offending cell back into line.
Early charging control systems were quite crude, and were designed to look for the battery being charged but they are installing better charging systems now.
