That depends on the size of the team but most of all it depends on the topics that need to be addressed. In few cases, it takes half a day to come up with a joint standpoint, a look back and a look forward to the prospects for developing a strategy, but sometimes it needs more time.
More as one or two days are seldom necessary to put a team process into place and to get the team running – certainly not enough, when one can presume that the team work will run smoothly and that problems can be solved in a collegial manner and not made worse, and that in critical moments, we speak with one another and not about one another.