Batteries are the one thing I don't take chances with.
Have my 1 month old Samsung 30Ts... bought 8... one of them acts funny and gets warmer than the rest... not like OMG its hot in my mech... but I notice it in hand feel temps... Marked it and don't use it anymore in the Overlord. Did a Internal Resistance test when I got them all, and it's a few points higher already, but nothing out of the ordinary... but the hand feel was enough for me to regulate it to flash light duty.
Have 6 more 30Ts arriving today, will IR test them, label the dates on them and charge-discharge-charge them as I do all new cells and put them in rotation.
Before I gave away all my VTC5A's to Steeldriver (and a few other cells) I tested them each month, some of the 5As even after 2 years of service only dropped to 4.14v fully charged, but I would 1.5A charge those cells... never did low and slow charging to see if they would charge further before being cutoff; like my 30Ts I charge them at .7a and they top off at 4.2v if I charge them at the normal rate of 1.5A they always stop at 4.19v... yeah I know a whopping 35mAh lol
Long story short... maybe in a regulated with low draw I might try to revive a cell depleted past 2.5v... but no way in hell would I for a mech... bad things happen to the cell chemistry when depleted below 2.5v... and $6 is not worth tempting fate