Picked the dental school with the longest breaks; used them as follows:
1. Christmas break of D1 year: threw a bunch of camping gear in the back of my old VW Westfaila camper bus, road tripped across the USA and spent a couple weeks banging around in the deserts of New Mexico /Arizona looking for Anasazi ruins. Very relaxing.
2. Summer after D1: packed a bunch of camping gear on the back of my old dirt bike and rode out to New Mexico, then two thousand miles off-road up the Great Continental Divide to the Canadian border along the crest of the Rocky Mountains; camped out all along the way; barely got back to school in time for the first day of D2 year. A most excellent trip.
3. Christmas break of D2: studied/took Part 1 boards, blech
4. Summer after D2: packed a bunch of camping gear on the back of my bicycle, flew into London Heathrow; pedaled north through northern England / across Scotland / across the Isle of Skye / took a ferry boat out the the Outer Hebrides, camped on beautiful deserted beaches and watched the sun set over the North Atlantic; barely made it back in time for start of D3 year.
etc etc etc, through to graduation.
Live it up now, while you can!!!! None of the trips above cost much of anything (note the common thread of camping gear). You can afford to do this kind of stuff if you rough it.
Sure, you will in theory be better able to afford vacations later in life. BUT: you will probably also have a family depending on you, employees, a mortgage, a practice note etc... at that point, other than little mini-vacations, you will not be going anywhere other than work. I am 44 now and can barely take time off.
You are more free now than you will ever be again.
Keep it frugal but do have adventures in D school.