In general, you can expect 500 full  charges for an 18650 lithium battery pack although this number can vary greatly  depending on the following factors.

• Physical damage by improperly mounting your pack is the #1 reason for short life expectancy. If you want your pack to last mount it right. (read a guide on mounting batteries.)
• If you are letting your battery pack get hot to the touch during discharge by running too hard, then your battery life expectancy can be greatly reduced. 
• The larger your battery in Ah the more power output it can take without getting hot.
• if you charge your battery to 80-90% you can expect to double the life expecancy of your battery.
• Consider buying a cycle analyst, which can be programmed to automaically charge your battery to 80 percent when you do not need a full charge.