Look at the valve seats as they are. Do you see smooth polished like patterns with no cracks or chunks missing from them?
Drop the valves into the heads. The edge of the valves should be sitting up above the surface of the combustion chamber. If you have feeler gauges, try and measure how much they are sticking up.
You really only have an issue if they are close to being even with the surface of the combustion chamber. There should be at least something like .030 or .040" of an edge, i.e., the valve surface being higher then the combustion surface.
If they are even or close, then there is a case for valve seat inserts.