I have my timer set to 4 minutes right now, and that typically leaves me ample battery for an extra go-around if needed. This flight ended up being almost exactly four minutes from take-off roll to touch-down, and as I recall, I believe I still had about 33% battery left. My flying style is such that I typically back off the throttle after reaching altitude, and just enjoy cruising around. As Dap suggested, start out with 4 minutes, and see what your battery level looks like after you land. If you prefer flying at higher throttle settings, maybe drop your timer a bit for that first check (better to land with a lot of battery left, than to be away from the runway when the battery reaches barely enough to keep the receiver active). and then adjust your timer accordingly.