i testing the same with "gustom item" >> "forum access"
hoppe this work, and remove the user-acess after 1 day.
so i can use this one for time limitet access.
i have to wait 1 day for check if it work.
maybe your answer here is quicker
anyway.
the easist way to use timelimit for usergroup.
make a addon for the vbulletin (Paid Subscription)