No do overs is setting yourself up to break a rule real quick and I believe is more about his insecurities than anything else. That is very natural and common with first timers. Again try it if either is funny about over conversation then it stops but why set yourselves up. Just communicate to each other a lot about how you feel and desire. Do this as a couple and see where it goes you can always experience more, slow down or stop.
Just my opinion with what I know