Don't worry, we don't all HAVE to be on even at all tomorrow, but we need at least a few people to be available for at least a while tomorrow, and wether it be the same people or different ones, a few people the day after that as well.
Basically, as long as there's available opponents for people to challenge, and nobody goes missing for weeks at a time, it'll work out.
You do NOT need to be available every day, or all day at any time, as long as you're present enough to keep multiple challengers waiting for a match with you for several days.