When is it ok to start talking to another team for next season

Why wait for next year, if you want out talk to them now and move 2nd half of this season.

ASAP! This is Jr hockey, you got kids coming and going everyday, just be sure you know what you signed with the current team

This doesn't apply to NCAA, but at any other level I say ASAP! As we know, AAA teams are probably 90% set for next year, already. In Junior, I suggest you get in contact with target team(s) to (a) gauge interest, and hopefully (b) spend a week or two with the team and/or (c) get in some games as an affiliate player. Now is the time for that.

Find a team that is loyal to their core players