Paul,
... how long can our .io group sit idle without being removed (if
that's a possibility) before we need to do something about making our
move and occupying it?
There is no time limit that I'm aware of. I held a couple of placeholders for over a year before initiating the transfer.
That's not saying that Groups.io won't institute some sort of policy for placeholders, if there gets to be too many of them.
Shal
Shal Farley