Campus Visits: When? Before writing application or...?

I hear you..I don't think school visits when classes are not on in full swing are even remotely as effective as those when the entire student body is around.

I would say that broadly speaking, you would be able to gather a 'sense' of your fit with any school by speaking with alums & current students, reading school websites & blogs by adcoms & students and other anecdotal evidence. Based on this, you would more or less be certain of a bunch of schools. You can always start writing your essays and be done with a major chunk of that work before you start your school visits. Once classes start in fall, you could schedule your school visits and then use your experiences to fine tune your essays. I don't think, or at least I never felt, that a school visit can help you start writing an essay from scratch; in my opinion, it can only help you tailor your essay for that particular school..

You might like a school more than or lesser than earlier after a school visit. In any case the ranking or prioritization of that school within your target list might change. I don't think you would ever regret having decided to apply to that school without having visited it earlier..

Further, you could split your school selection into R1 and R2 such that you have sufficient time to use your school visit experiences in modifying your essays for all schools.

So, all in all, I think you have good time on hand. If you can manage to shortlist your schools, prioritize them and be done with writing a major part of at least your R1 apps, you should be just fine visiting schools after classes begin in Fall.