How much video record time do I have on iphone6

Your basic limitation is how much free storage space is left on the phone (found in Settings / General / Usage). How much time does each GB equate to depends on how you are shooting. The i6 shoots at 30 fps by default but can be set to do so at 60 fps. Plus you can shoot at regular speed or slow motion. Unfortunately, Apple does not publish exact specs on the device manual, so you'll have to do some test shots and see how much they take and extrapolate from that.

BTW, the iPhone 6/6+ manual is found here (or you can download it for free in the iBooks app)