Your average name brand NiMh battery is a 300 cycle affair. That means the maker calls the battery good if it can get to 50% capacity after 300 uses. There are cheaper batteries that are worse than that. As to the time left according to the camcorder, since it's not the camcorder battery maker's battery we can't expect it to be close to accurate.

For me the big clues about battery replacements is the size and weight. If it's the same size and weight I expect close to the same as a new maker battery. And by close I mean within 50%.
Bob