I wouldn't trim them and they will get a whole lot bigger. 7' isn't very long for a passion vine. If you trim them you'll probably sacrifice blooms. The only reason that I'd trim them is if they are looking lanky. Mine seem to bloom better being a bit root bound. As long as you are getting good growth and lots of buds I'd leave them alone.
Karyn

Thanks Karyn, they're doing fine outside, aside from a bit of sunburn on their tender leaves, and are growing darker more robust ones. I can't wait till that "wall" is covered with flowers. I think the potbound issue is what I was waiting for with my red one which barely bloomed last year. Now that it's good and potbound it's going nuts!