how does k2 handle incomplete or suspended or left process instances?

Strictly speaking, in K2 there is no such thing as a “left over” process. You must remember that the engine sees the process as either active (still in progress) or completed (without going into the other statuses). It is impossible for the system to determine when a process is “left over”, I have seen cases where instances are kept alive (by design) for 180 days after it has been logically completed.

If you need to do something when a process has not been completed in what your application deems as a valid period, set a process escalation to do some housekeeping (email administrators or expire the current activity, etc).

Thanks DC

it is really a good approach