We usually did weekend trips, trying to see two colleges per day in the same city - but obviously less, if they were a distance away: We would see Boston U and NorthEastern the same day in Boston, or UMass and Amherst the same day, or Georgetown and GWU.
But, when going to Williams, there was nothing else in the Berkshires to combine that with.
Anything longer than two days, I would certainly build in a buffer - because I fear there’ll be diminishing returns. At some point, it will all turn into a blur and/or the last few colleges won’t get a “fair share” anyway because everyone’s “so over it” by then.
I remember my daughter going with a few peers and one of their parents on a multi-day trip - and they started skipping a college the last day, because it was just more input than they could process.
It did help her, though, to figure out some early selection criteria, as far as urban vs. not, large vs. small. But a year later when acceptances came in, she had to go back because she really couldn’t remember one from the other - or what she had liked about it to make her apply there.