Hey I’m a final year Durham student. It depends if you’re actually going into each college or just looking etc. If you’re looking solely at the Bailey colleges you can probably view most as they’re all along one street. Likewise, if you’re just interested in the hill colleges you could see a few in 2 hours.
Speaking from experience, your college can heavily affect your overall experience at Durham. It’s much easier to build relationships at catered colleges as you’re eating with the same people every day & it’s a tighter knit community. Colleges still run events after first year (formals/balls etc) so you still feel involved even when you move out.
Some hill colleges offer limited accommodation after first year which you can apply to.