^ I think I'd rather have a little smoke at startup instead of that burden or expense.
I'm JUST NOW thinking about replacing the over 10 year old air filter on my B&S v-twin 19 HP intek engine in a mower. I have brushed some sediment off and banged it to remove some dust yearly, over the > 20 year period where it's on air filter #2.
Valve lash adjustments really? I guess you can spend as much as you want to. I never needed to do anything to this engine over the 20+ years except tighten the flywheel bolts once, and of course, change the oil/filter with nothing special, any major brand 30wt.
No good reason to pay more for 5W-30 synthetic unless it's a snow blower or water cooled engine... which it might be!
Granted, my lower standards could be due to only mowing 1/2 acre in my climate, you could be putting on more hours per year, but even so, I don't see the justification to treat a mower like it's your first born child if others don't have problems spending a fraction as much time or money. Except, this is BITOG where maintenance has nothing to do with need and everything to do with excess.