This depends on how long your pumping sessions are, and how intense you like your pump suction to be. Fully charged, the battery lasts approximately 2 hours, so most users will get 12 x 10-minute sessions per full charge. Then it takes about four hours to fully charge, but a quick charge is good for one pumping session. When the pump is fully charged, the blinking red LED will turn off.
If you want to know how to check your battery level, check this article.