One of the reason I challenge other teams to scrimmages at my home court is that it is the default option.
I usually challenge other teams to scrimmages before Saturday night, 8 hours after the scrimmage challenge is available. I don't challenge teams that haven't scheduled scrimmage before. It would waste the challenge offers since we can challenge at most 15 teams at a time. I usually challenge 12~15 teams, then take a rest, waiting for some team to accept the challenge.