Battery question

I have some rechargable Lenmar NiMH batteries (2000 mAh, AA) that do not
seem to hold their charge. Even with no use whatsoever, they seem to be
dead a day or two after a full recharge. I get only a few minutes of use
from them when I put them in my camera (Nikon Coolpix 2100) after a full
recharge. I think I recall reading that batteries hold their charge better
after they've been recharged a number of times, but these batteries have
been recharged at least 10 or 15 times.

My questions: Is this the sort of thing that varies from brand to brand in
NiMH batteries? If so, which brands are best for retaining their charges
and not draining too quickly?

Thanks.

JEP