The main charging difference between NiCd and NiMH is that the NiMH has a much more sensitive peak. Many older NiCd peak chargers will miss the peak, and continue to charge the pack until it burns up.

Your experience tells me one of two things:
1. Your charger is a newer, more sensitive peak detect model.
2. You have a fixed-capacity, or timer-driven charger.

Be aware that NiMH do not hold up well to being overcharged. You should only charge them with a peak detect charger because that's the only reliable way to tell if they're fully charged. Anything else is just guessing, and could be a problem.