Except for Arches you can easily spend weeks at any of them. We have over the years and look forward to return trips. But it depends on your visiting style. Do you want to do a thorough exploration, or are you happy with something less than that.
Zion has been somewhat ruined by the mandatory bus shuttle system now in place. That cuts down you ability to explore as easily as you once could. Arches and Zion are both darned hot during the summer.