I am a fluent player on skyblock and on all sides of my island are dead islands that players do not go on. For some reason or another they just left the island. Now all I can see is little starter islands with nobody ever on them. I think that if a player is not on there island for a determined amount of time that there island should be removed so that we active players arnt having to look at these dead islands all day.
Then again, there may be difficulties with the system. If the set time is, let's say, 2 weeks, what about someone who goes on vacation? How could island size affect when it is deleted? These are a few tough questions that need to be answered before a system like this could be put in place.
Well when it comes to vacations you can simply notify and admin so they can increase time for that specific island. And I don't think island size would effect it at all.