I tend to see little movement in the vavle clearances of all the bikes that I regularily maintain for customers. If I was riding a long trip, say 10k total, I wouldn't bother with checking/adjusting valves until back home. Oil changes are involved if you remove all of the screens and filter, are technically possible to perform without removing the left fuel cell.
For my bikes, total time between oil changes depends on terrain, riding style, temperature. When on a long trip, I have stretched out my change interval to 5k miles.