How long to seat new rings?

I bought a 19,000 mile winter project bike. It calls for 6000 mile adjustments. The valves had never been adjusted.
The bike ran and shifted nice once warmed up with no smoke blowing on acceleration or deceleration. It felt strong.
I thought I'd check the compression before checking the valves (push-on type tester). Three cylinders were low, one cylinder was real low. Not good.
So I checked the valves all eight were way out of spec. Two were acceptable, three were almost tight, three were so tight I couldn't get any feeler gauge in at all. The tightest was on the offending low compression cylinder. 
I adjusted all the the valves to the loose end of the spec.
When my friends asked me if I rechecked the compression, which would surely have improved, I told them NO!
I didn't want to know. The bike starts and runs perfectly, it's quiet, there's no smoke at any RPM and it feels at full power.

Moral of the story... If I'm happy the way it runs and is not showing signs of trouble..I'm not gonna go looking for any.

Did you use a synthetic motor oil?
Or did you use a break-in motor oil?

I used conventional. Dont remember the exact type but it was per Joe at Pit Stop Performance's recommendations. He did the block, pistons, and rings for me. 

Okay so valves were mentioned. When I had the head set up it was for 3X cams, .418 lift and 282 @ .030. I never put these cams in. Instead I put K410's in, .410 lift and 266 @ .030. A slightly smaller cam. Could this throw the shim clearance off enough to keep the valves from seating? Seems like it would have the opposite effect and make them looser. 

Always, always, always check the valve clearances after a rebuild.  Trust nobody.  And torque the head every few heat cycles until you stop seeing torque falloff.

Higher/lower lift cams won't affect clearance because that's all about the base circle.  And aftermarket cams typically run looser valve clearances too.