I use a S800, Zenmuse and 5.8 Vid DL with a NEX5n.
I get about 10-12 min on dual 5K lipos, and 12-15 on dual 6k. I don't have the DataLink, OSD, the FPV cam or retracts. So your time seems about right.
Also it is temperature dependent. Cooler temps shorter flights unless you have away to keep...