Back in 2004 when I first started using LiPos I would test my batteries with a 1 ohm resistive load. On a 2S battery the current with the 1 ohm load is typically around 6-7 amps. The graph beow shows tests of a 2S Kokam 1500 mah cell. You can see that the load corresponds to about 4C. The battery was rated at 10C so thats about 40% of the rated C. The battery was used in conventional RC and was flown until the esc cutout which was about 6 volts under load. Thats an extreme use of capacity, not recommended in hindsight.

From the graph you can see that the 50 flights reduced the available battery voltage and the total battery capacity. A rough estimate is 15% loss of capacity and about 0.25 in typical reduced voltage. Another feature is the extreme loss of voltage at the start of the tests. I could observe this in flight and all packs that were flown a lot showed this phenominum. After this initial sag the battery would recover to a reasonable voltage.

This battery is OLD technology and modern batteries should fare better. But it gives you an idea of how a liPo ages.