I partially agree with it.
Premium ressurces should get a label/tag that is called "Inactive"  when there hasn't been an update for 3 or more months.
The authors should be able to label/tag their premium ressources manually or they are tagged by an moderator, when the ressource is reported by people who bought this ressource.

The inactive tag should NOT be an indicator or synonym for a not working ressource, but should give potentially buyers a heads up to reconsider the purchase, because there is probably no support.

Yes I am aware that there are premium resources that have been updated one year ago and are still working fine, because of this, "old" premium resources shouldn't be tagged automatically, but manually by a moderator when the ressource gets reports.

But: At least I am one of these guys that are monitoring the activity of the plugin author before purchasing and even when he is pretty active, that could change every day.
I try to buy only premium plugins when there is a source provided or it's 99% sure that they don't break with newer spigot versions or are working in general.

So the tagged label would be more a little help to consider if a plugin is active developed or not. But nothing more.