For the batteries to last for years. No they don't. You didn't do anything wrong but the makers didn't tell you to expect at most 100 cycles from said batteries. Get the same or more mah batteries (yes I know you didn't want to hear that) and when the life runs out, replace them. In spite of a yearly replacement these can be cheaper than alkalines and from what I read still more eco-friendly than one time use batteries.
And no, you can't avoid this. Battery technology at this price does not give you a many year battery.
About 10 months ago I got a Sanyo AA battery charger pack with 4 2700mAH NiMH batteries for my new camera. I charged them up and they kept the camera going for an entire week. But they started holding a charge worse and worse. Now I can charge them all the way and the camera will work for 10 minutes. What happened? Did I buy bad batteries? Bad charger? If so, how do I avoid such things in the future? Is there a way to get them back to where they were? If not, what batteries would you recommend that I can get relatively cheap? Do I need a new charger too?
Please be as specific as possible with exactly what batteries to buy. I don't need general tips like "more mAh is better."
I think this is what I bought before: