Perhaps I got an outlier, but my 2020 SRS has around 48k miles on the battery and its capacity is so close to what it was when it was new that I dont see a difference. Its used hard too, each way back and forth from work has extended high speed riding with me and 50 lbs of gear
BUT, there is a way it degraded, which is that its less resistant thermally to high speed. When new i could ride through a whole charge going as fast as the bike would go, so fast that the motor thermal limit would kick in sometimes. Sometime around 30k miles it changed so that just riding at a steady 95mph will overheat the battery and make it cut my speed. 90 is ok. Not a big issue, but there it is.
The second thing I would look out for is warped/cracked front brake disks. I went through 4 OEM disks in the first few 1000 miles before switching to a set from EBC, which then lasted 40k+ and are still fine.
The third thing is that at least some of them have a flaw where if water gets into the air cooling channels of the charger(s) it can cause an isolation fault. I didnt want to take mine in for that because its in daily use, so I made a little shroud over the air intakes from coroplast that keeps the rain out. Some people say they had theirs replaced with chargers that dont have that problem.
The fourth thing is try to see a paired app and see if the cellular reports. Mine quit, but I dont care. I ride back and forth from work. I know where it is.
And lastly in general look it over closely. They are made with a mixture of high quality and low quality parts. The plastics are brittle, the paint is cheap, etc. Look closely.