You won’t find out unless you try! Just keep doing it until it stops being fun! And going over by accident, as long as you ruin it, doesn’t end it. Don’t worry. Gosh, from five days to 15… quite the leap! (Don’t forget your family will still want to see you in between all the orgasming on your birthday!)
PS Maybe you should ask for some Lovehoney gift vouchers for your birthday… it seems topical!