i'm so happy to have found this board....it's just so frustrating that it seems like there are almost no definite answers!
I'm about to muddy the water even more...It is certainly possible for an individual to be "coinfected" with more than one type of HPV ("high risk"types and/or "low risk" types, doesn't matter). I don't know if the exact likelihood of this is established, but it wouldn't be rare.
HOWEVER.....remember that most HPV infections don't seem to hang around, as the immune system can usually clear/suppress them. The virus may not be eliminated, but probably becomes latent in small quantities within deeper skin cells. It hasn't been proven that such a suppressed infection won't be given to a new partner, but experts think the risks of transmitting an HPV infection probably diminish greatly once somone goes a year or so with no more lesions detected (wart or cell changes).
So the question "Can he have more HPV, or more than one type?" doesn't go all the way because even if he has a history of having one or more HPV infections, he may not have them now, or they may be latent and not likely to be transmitted. Where I'll fail you in all this is here; there isn't a "test of cure" where you get official results that say for certain, "Ok, it's gone, no worries." Bottom line is long term persistence isn't likely, but proving it remains hard to do.
Hope this helps,