@Napa Paul wrote- "My mechanic will check the valve gaps and if they NEED adjustment - the way it's running, I doubt it - he'll do so. As far as I'm concerned, whoever built this engine for Kirk in 2009 sure did a good job!"
Glad to hear your engine runs well! Regular maintenance goes a long way with our little antique wonders.
You'll probably find that generally they don't move much and only the odd gap needs minor tweaking. That said- I wouldn't stray too far from the factory maintenance recommendations (which is to adjust the valves every 3,000 miles) if only for peace of mind. A regular valve adjustment gives you a window into the health of the valve train- minor adjustments are normal and tell you everything is wearing acceptably, where as a sudden large gap will warn you of parts wearing much quicker than normal, and what to look out for. I'm thinking a pushrod tip pounding into the pushrod, the tip itself wearing unnecessarily (neither are anywhere near common but do rear their ugly head occasionally), or if it's 1 loose on each side (along with some silvery slur in the oil) a lifter/cam lobe may be grinding itself into oblivion. Adjustments tightening up more than normal are also a warning, as Greg and I mentioned above.
The point is- regular valve adjustments will catch these things before they become a problem that wipes out most of the engine. They'll still cost money and time to fix, but you won't be buying everything but the carbs, manifolds, header, distributor, engine sheet metal and fuel pump. You can't rely on just your ear to tell you when it's valve adjustment time- a lot of things have to get surprisingly bad before you can hear them.