I have a Panasonic cordless phone that came with a NiCd battery. The battery failed within a year, as NiCd cordless batteries usually do. I found a NiMH substitute, designed for a different Panasonic phone but with the same voltage, shape and connector. So I installed it.
The NiMH has a better lifespan per charge than the NiCD ever did. As to how long it'll last, I can't say, because I forget exactly how many years it has been since I made the switch, but it has been several years, and the NiMH battery is still going strong, maybe just beginning to show a few signs of age. On the other hand I've never met a NiCd that I really liked.
There are some differences in the ideal charging parameters, but to a considerable extent, they overlap. Of course Your Mileage May Vary.
-- fred "at" ionary.com