Originally Posted by Matt Price
There should be a rule in place to have the rosters of non-playoff teams locked through the end of the playoffs, but if there is no such rule then you are well within your rights to make a move.
Not sure I agree with that first point, especially if the provider shuts down after the season. If it's a keeper league, teams should have the right to make changes at any time during the season, regardless of whether they're in the playoffs or not. Playoff teams take on the risk when going for the title.