You're probably in good shape already. I usually try for 20 to 30 minutes at 2,000 RPM for cam/lifter break in. The first few minutes are the most critical, as the cam needs lots of lubrication from the oil being thrown off the crankshaft. The high idle speed helps flood the cam in oil thrown off the crank and rods. It might be a good idea to re-run the valve adjustment before you button everything up for good.
Jerry

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