dude, your gonna have sex with her before having her suck your dick to completion at least once?
That in itself should solve your problem, once she swallows your load ( or spits I guess, Ive heard of this happenning ) then tell her to get you a smoke and a cold beer.
Once you puffed and tanked that cold brewski your ready for round 2.
Of course at this point she will enjoy it a lil more cause you wont cum in the first 2 mins lol...
When you ready to drop another load pull it out and jerk off all over her tits, then make her rub it in while she moans...
your welcome