[GuidoK]

Yes a leakdown test never hurts. Although leaks can go up (valves/stemseals) down (rings) or sideways (gasket). but its a first pointer to look for faults non destructively

But regarding removing the head: if it aint broke..
Removing the head is never without risk. Now it fits snug, but under tension. Remove it and the tension might result in warp requiring a skim. And refitting a different head gasket might not have such a long life, aluminium head on steel block is always difficult.
This current gasket/dir obviously is a good one looking at the miles.