NiMh should get pretty hot when they peak, temp should be 120-125F. If the charger says they're charged, be sure that they are hot. Otherwise, its a false peak where the charger thinks they're charged. If they're still cool/cold, just reset charger and charge again. I've had packs where I had to do this more than once to get them to charge all the way.
Packs that have been unused for a while might need some cycling (repeated charge/discharge) as mentioned. If they don't run long, let them cool and charge them again. Look at the mah put into the pack by the charger, if the packs are getting better, this number should be going up.
What capacity (mah) are your packs? That's usually needed to determine what charge rate you want to use. I run 4000mah pack with my old Emaxx and I charge them at 5amps.