Oil breaks down (shears?) with use. It's not unusual to notice the engine working harder than normal with fresh oil.
I've had a dealer do a valve clearance inspection on a 7th gen 4 cyl Accord at 50K about three years ago. The dealer charged an hour of labor for the adjust. Typically they adjust rather than inspect. Unless you ask for it and pay for it, a tech won't make any measurements or record anything. They will select a feeler at the center of the clearance spec, loosen the adjusting nut, insert the feeler to establish the gap, then tighten the adjusting nut with the feeler in the gap, then check the gap.
I take 4-5 hours to do the job myself, but I spend a lot of time measuring, messing around, and cleaning parts. The job is not difficult if you have a factory service manual and watch youtube videos.
The engine should be cold. Usually that means letting it sit overnight. I also think if it is too cold outside, the clearances are skewed and for certain RTV sealant takes forever to cure. So do the job when air temps are in the 65 to 85 range.
Amazon sells a handy tool which makes tightening the adjuster (while maintaining the gap) a lot easier. I could find a link...
Because of the now famous issues with the 1st gen CRV, I check clearances first at 50K and then every 30K. Some of the clearances have been tight but within spec. I always center them. Never notice any difference in noise or driveability or economy.
I called some local dealers a few weeks ago for quotes on an inspection/adjust. The results were all over the map. I'll try to post that info later.