I think the sooner the info is out there the better. It helps people plan. People want to take vacations after the season, kids that play rec are making decisions about all-star teams, etc. The more we allow people to make informed decisions the better.
That said, get listed on the tryout board, post a thread with more detailed info and be done with it. No need to bump your 2015-16 tryout thread ever 2 hours 6 weeks out from tryouts. For that matter, there's no need to bump it 6 days from tryouts either!