I have 8 RN4072 batteries. One of them is very hard to draw on (like a delayed reaction), the rest are all normal, hold a charge the same (short!) time & charge in the same amount of time.
Main problem I've had is I've gotten liquid into them. If a battery is not performing well, I use tightly rolled up corner of paper towel & put it into the hole on top. It gets the liquid out & all is well again.
Honestly though, if you get a batt and it's not working right within the week, drop an email to the vendor. I haven't found one yet on ECF who wouldn't work with me when I've had issues.