How do I mark a job complete when the buyer has no recent PHH activity?

There's been a similar question asked, how do I mark a job as complete?, which PPH mods have marked as answered.

However, it only goes part way to addressing the problem of stagnant 'In Progress' jobs for sellers.

As sellers, we're duty bound to mark how many projects we can take on at a time.

But what can we do when buyers who show no signs of recent activity on PPH have failed to mark a task as complete?

Do these redundant tasks, which we as sellers cannot bring closure to, count towards the number of jobs our profile shows as 'In Progress'?

And what flags have PPH mods got on the system to identify tasks that are technically still 'In Progress', but have obvious signs of closure due to inactivity over 'x' amount of time?

If I've been wasting my time and proposals because I have five finished-but-not-technically-closed assignments when my limit of concurrent jobs is only three, thus buyers aren't awarding me jobs due to unavailability, I'll not be a happy bunny.