I've got a Galaxy S3, an S4 couple first generation Moto Gs, a 2012 and a 2013 Nexus 7, a Note 2, I think? 2 Note 3s, and a One Plus One in various states of: loaned to cousins, used as house phones, backups in a drawer, backups in cars, or lying on my desk.
They were all either broken, at yard sales, given to me my clients / contacts that don't want them, or were In general four things kill these devices:
* Touchscreen breakage. It is almost never worth trying to replace if the screen cracks.
* Flash burnout. Shitty flash chips don't last forever. I've binned almost every older phone than this crop because the flash memory dies.
* Charger port wear. Microusb sucks, replacement parts vary wildly depending on model - I can get an S series charger for * Software. I generally outright ignore devices without a ROM scene and an unlocked bootloader, but even then it is entirely volunteer how long Cyanogen/Lineage/Paranoid/etc are willing to keep supporting these fossil kernels. The S3, Note 2-3, and original Nexus 7 are all on their deathbeds because of lagging community support for these devices. It is worth mentioning, however, for the Samsung devices they have gone community supported far longer at this point than their official support periods lasted. Great job Samsung.
Batteries are usually a non-issue. You can buy shitty Chinese knockoff batteries (or if you are lucky Anker) that don't hold a charge and don't last long, but you can keep these devices running on bootleg parts for a while.
The software is the ultimate killer. What should be the easiest to maintain is the hardest, because corporate greed and hunger for control trumps customer respect. All my mobile devices are cheap, used, or broken when I get them because none of these exploitative abusers are worth giving a direct cent to.