Have been using IP Lipos for a couple of years now, in 50c and 60c. Superb, can't fault them. Good performance, great price, and no reliability issues.
As with any Lipo, always store half charged, balance charge regularly (every run if possible), and let them cool before recharging. If you do this they'll last for years.
RC-Timing Software - http://www.rc-timing.com
Mercedes AMG F1 - http://www.mercedes-amg-f1.com/