Its strange, when ever i spank it, i always try to do it in record time. But when it comes to sex, i can last an hour before i get more and just want to release the pressure
Only advise i can give is jerk off a little while before you have sex. I remember reading something that you should try spanking it for about 15 to start, then each time your about 90% about to spew, stop for about 15 secs to a min. Once you get good at this, increase the time.
Its also a mind game, since this was a new chick, you probably were horny out of your mind and wanting it all day. This for me seems to really decrease the length I can go for.