From mahaenergy.com:
The Powerex MHRAA4 Rechargeable AA NiMH Batteries (1.2V, 2700mAh) - 4-Pack is a package of 4 AA nickel-metal hydride (NiMH) batteries. They have a voltage of 1.2V and a capacity of 2700mAh. The batteries can be recharged hundreds of times, and because they have memory-free operation, they will not develop memory effect, which can cause batteries to hold less charge. These batteries will retain a charge at or near their full capacities even after hundreds of charges. A battery carrying case is included.
Nickel-metal hydride (NiMH) chemistry.
Voltage of 1.2V and a capacity of 2700mAh.
Batteries can be recharged hundreds of times, and because they have memory-free operation, they will not develop memory effect, which can cause batteries to hold less charge.
These batteries will retain a charge at or near their full capacities even after hundreds of charges.
A battery carrying case is included.
I would say that your cells did pretty well if you were able to use them 500 times. Depth of discharge can also affect the life of a cell. Typically the deeper the discharge over and over again the shorter the life in cycles. It sounds like you treated your cells well to make it to 500 cycles.
I think you have gotten the advertised life expectancy out of the cells, so not correct.
Eneloops, Powerex or Tenergy. The key is to purchase cells that match how you will use them. By that I mean purchase cells that capable of delivering high-current in high current applications and purchase cells that can deliver more mAh at a lower current draw over a longer period in low current applications.