Son visited ~8 colleges/universities (1 of which he wasn’t really considering, but was tagging along with his girlfriend’s family), applied ED to 1, was deferred, applied to 4 more, accepted at 3 (including his ED choice), attended admitted student programs (re-visit days) at 2 (including his ED choice), ended up going to 1 (his ED choice).
Generally through the process, whichever one he had visited most recently was his favorite. Not sure if that was because it was freshest in mind, or if that was just how it happened to work out. (The exceptions were the one he visited with his girlfriend’s family, and the one we visited after he had already submitted his ED application, as an additional possible back-up choice, which he did end up applying to.)
All of the visits were individual trips, with one in fall of Junior year, most spread out over spring of Junior year and summer between Junior and Senior year, with one in the fall of Senior year.