Rapid charging partially discharged NiCd batteries is a direct cause of the (so called) "memory effect".
That's why we switched to a peak charger as soon as they became affordable. They're specifically designed--so sayeth the literature--to avoid that. We did notice quite an improvement in battery life after moving away from the simple 15-minute jam chargers we had been using for the first few years of using NiCads. That practice definitely led to overcharging which I'm sure led to the premature death of a number of our battery packs. The reality is dad's got locos with 20-year-old NiCads installed in them that still hold their charge quite nicely. But I hesitate to hold them up as an example of battery life because they run three, four times a year at the most. Some probably don't run but once a year. If anything, they serve as an illustration as to how long the battery technology can be dormant and still work.
The question you have to ask yourself is how often do you realistically run your trains? How many times a year will you actually charge your batteries? If you only get out to run trains once a week, even assuming you do that 52 weeks a year, that's 52 charge cycles per year. Personally, I'd love to be in a position to run even half that often. I probably cycle each battery pack 10, maybe 15 times a year at the most. Rated at 500 cycles, that gives me 30, 50 years? Perhaps in theory, but my gut tells me I'll be swapping them out before then.
Later,
K
