XF 1.5 Change usergroup based on inactivity

[Unity]

I'm currently looking for a way to do this but can't seem to find any plugins or resources from xenforo to do it.
Does anyone have any advice or a method to do this?

Just to clarify, I'd like it so:

If user has been inactive for more than a month, they're added to an 'inactive' group which requires a staff member to rank them up once again.

 

[Martok]

You can use this add-on to achieve something similar to this:

https://xenforo.com/community/resources/cta-criteria.3006/

using the criteria "User has posted at least X messages in Y days"

Create a user group promotion for users who meet this criteria, promoting them to a user group with, say, more permissions and/or access etc. Any users that don't meet the criteria won't be promoted (or will be demoted from the group if they are promoted and later become inactive). It'll then be completely automatic and won't need staff members to manually promote users.