After Thanksgiving (at the earliest) means that CSL and SCDSL are over and many kids/parents have had at least one weekend off from soccer. We were naive when we setup our club initially and did open tryouts in Feb/Mar, only to realize many kids committed to clubs in Jan (some even earlier). Lesson learned. We usually have kids come out to practice with our teams once or twice and play in a scrimmage but not until December at least (and mostly not until the new year).
None of our existing players lose their spots on the roster until after State Cup so we don't often make changes before then anyway; the only way anyone leaves before Feb is if they choose to join another club (and that scenario hasn't happened to us before State Cup in the 3 years we've been formed). The only way any new players come in before Feb is if we already have an open spot. We carry a maximum of 16 players on our rosters and with a couple of teams having 15 this season, we do have one or two spots open for players that could essentially join from Dec onwards. I know many clubs carry more than that (and some carry less) but for me it's a playing time issue. Getting 5 subs playing time is tough enough; any more than that and it becomes a bit of a nightmare.
The tryout season and madness of it all is equal parts laughable and shocking. I understand kids and parents being unhappy with their situation and wanting to leave but for me there should be an element of making a commitment to a team and your teammates, then seeing that through (on the part of both club and player). Of course, if there are extreme circumstances (such as a crazy coach or the team not being able to raise enough players for games), it makes sense that you would want to move ASAP and break any commitment.
Tryouts get earlier every year and the whole tryout process seems to get messier every year. I don't know what the solution is, I'll be honest.