charge rates

As a general rule, what rates should 18650, 14500, 10440, AA and AAA NiMH batteries be charged at?

Rule of thumb I've read: optimal is 1/2 the mAh or less to prolong battery life. So a 2000 mAh 18650 should be charged at 1A, smaller capacity batteries should use the 500mA. That's the two settings on my Xtar, anyway. Always heard the slower the charge, better it is for battery life.