The "how many charge cycles" statistic can be misleading. If you top off your battery (which, as was said above, it is fine to do with K2 and K3 batteries) it does not count as a charge cycle... at least not a full one.
Let's say you use 10% of the battery every day and top it off every night. After 10 days of this you will have "used up" ONE of the charge cycles. (10x10%=100%) So if indeed the battery can handle 500 charge cycles (I've heard more) you still have 499. At that rate the battery will last about 14 years!
Enough about math. In reality, I've had a K2 since launch day and I give it a full charge every time it gets to about 50% (just because it is a convenient time interval for me) and it shows no sign of not holding a charge. I don't anticipate every having to have the battery changed.