If you doubtm then dont, at least for multi cell lights. I keep all my off-brand batteries in a grip top bag for emergencies so i can power my 1 cell lights using up the random semi used or new off-brand batts
I have used both their primaries and their secondary batteries with not a single problem. Several of my LiFe rechargeables are going on two years old now have have about 200 cycles on them, they are still going strong, holding their charge.