From my own experience - it's not easy, and hard enough for me to have never tried it. Maybe a few times after my first sex (which was with a rather hung guy), but I noticed quickly that I need more size to feel comfortable during sex. I'd not consider myself to be a hardcore size queen, but I can't relate the fun and pleasures big cocks give me to smaller men, and I can't see a good reason therefor why I should try to go back. If you know what fun you can have with a big dick, why give it up?