We actually have 3 day trials on our sites. We don't that have that many upsells in our members areas and we also give free access to other sites when members join. The free sites are not crappy sites but very nice sites.
So when a member joins HSBoys they also get access to Broke Straight Boys, Straight Boys Jerk Off etc. Those sites has no upsells at all. We can offer 3 day trials with great members areas and we have really good retention. Sure we lose those customers that just go in and download videos and then cancel but the majority stay as members because they really like the sites. We might even lose those customers but some of them even come back again and again.

I think the other way to offer 3 day trials is have a crappy members section with tons of upsells where they don't care about retention. This method doesn't make sense to me but I have seen it done alot.

Mark