Info sessions during school for a big state school may not be worth missing class. But for LACs, often the rep is the same person who will present your child’s app to admissions. Both my Ds have had one-on-one sessions. D19 is considering ED to Dickinson and will certainly meet with that rep when she comes in October.
I agree the ideal time is when student is a senior. The rep you see as a soph or junior may be gone (grad school, now job) by your senior year. But that senior year, maybe the college you like sends nobody. We have some colleges that come to my Ds HS and literally no one shows up, and those schools don’t return.