I'd say 10dpo if you've tested early in the past. At least, that's my magic day when I've gotten a BFP each time. 7dpo is super early! A lot of women start at 12 or 14dpo.
big boy 12.8.07 @ 39+2 7lbs 8oz, 20.5" BFed for 13 months
middle boy 8.12.09 @ 39+4 7lbs 9oz, 21" BFed for 13.5 months
little boy 4.26.11 @ 38+4 6lbs 14oz, 19.5" BFed for 26 months
baby boy 10.25.13 @ 41+0 8lbs 15oz, 21.5"
8.16.12 & 12.16.12
10 DPO is my earliest also... That's not to say I haven't POASd earlier, but 10 is usually when I try to hold out for. But even then I keep in mind that it's super early and could still be a false BFN. Good luck!!