How many miles before checking plugs

[blown motor]

The engine was running slightly rich according to the plugs so I changed the rods in the carb to lean it out a wee bit. How many miles do I need to put on before checking the plugs again to get a good read on things?

[RUNCHARGER]

Oh man: I'm going through this right now with my bike. I pulled them at 50 miles and they were too white for my liking. Last thing I want is to seize an aircooled engine. So I richened it up and pulled them at another 100 miles. I think these ones read great for an engine with 55,000KM on it. I won't be reringing this one.
If it's not running strange I'd give it 200 miles before looking at them I think. 200 miles should give it enough time to burn off the previous deposits from the rich condition. I also would try to make the 200 miles in only 1 or 2 cold starts if possible. I know sometimes that's not easy to do.

[three two barrels]

Take your car out on a deserted highway and give it some fairly aggressive throttle bursts and then pull over and pull a plug and see what it looks like, should give you an accurate reading.

[blown motor]

Take your car out on a deserted highway and give it some fairly aggressive throttle bursts and then pull over and pull a plug and see what it looks like, should give you an accurate reading.

We don't have deserted highways, but we back roads, and they're paved.