Hi,
According to that data sheet, the cell is supposed to last for more than 4 years with a constant charge of 0.05 C and if it stays under 55 degrees C and under 65 degrees C only once in a while. It may also require what they call "Maintenance" which means discharging completely every so often so that the cells do not develop what they usually refer to as the "Memory Effect", which causes an apparent loss of capacity.
Since 0.05 C isnt that high (100ma for a 2000mAhr cell, 200ma for a 4000mAhr cell) this could be acceptable data. The truth of these things comes out when you actually use them. If you are prepared to buy new cells you wont be disappointed
Which makes me wonder just how much these cells cost you that you are so worried about this. What if they only last 2 years, is that going to be a big problem?
I used 2Ahr rated NiCd cells for years. I found that the charger that came with the unit i bought did not function the way it should so i designed one. Since the cells were not used very much (once per month perhaps) the main idea was to just keep them charged so that when they were needed they would be ready to go. I found that the only problem was to maintain a current that would overcome the self discharge of the cells over time. But the other problem was that the required constant current was too low to be deemed effective, so i had to build a charger that would pulse the NiCd pack twice per day with enough energy to keep them primed and ready for when i needed them. The charger pumped a regular level charge (like 150ma) for a short time period, twice per day. That was enough to keep the cells ready. The cells lasted for five years.
After that, i gave up on NiCd's because i felt that i would have liked to get more life out of them over the years even though i got 5 years out of them. So i switched to Lead Acid. Lead Acid have their own problems, but they are cheaper for the capacity you get and i need a lot of capacity. The NiCd's were not really that great anyway at only 2 ampere hours. Lead Acid batteries are readily available at huge Ahr ratings and they also supply more instantaneous power, so i went to those. My main application at the time was power tools, but now it's expanded to a lot of other things too so i go with Lead Acid now.
I also use NiMH for some small applications like flashlights and small emergency lighting, but i only use the low self discharge type because the others loose their charge even over short periods like a week or two. Just to note, the NiCd's you use loose about 35 percent of their charge over a one month period.