A guy i worked with told me you have to flush when you change oil no point on doing oil change argued that regular oil changes thers no need no he was right until he did his newly purchased orion.The subject wasn't broached for a long while after that.
I have always been told...on older cars, not to flush, so I never have, never seen a modern engine that has failed for the lack of a flush.... have you? if it ant broke..............
How well do you know the engine?
How long have you had it?
How often have you changed the oil?
What oil is in it?
If it's a fairly new engine to you then it might be worth taking a rocker cover off and having a look. If you still can't decide then do another oil/filter change after a couple of thousand miles and see what comes out then.