If you're worried about valve life, not terribly concerned about environment, I saw 'real lead' additive at parts store the other day...tetraethyl lead over the counter- dont get any on you!
a dab in the tank occasionally could be alternative to putting stainless seats in your motor. you could probably replace 'umbrella' valve stem seals easily by yourself for minimal cost- wont help worn guides, but should slow oil consumption.
might also suggest looking at spark plugs- one oily plug might point to a vacuum leak under intake port, or possibly worn out camshaft- I had a 396 chevy i got for cheep, had 3 wet cylinders- found those three cyls had near perfectly round cam lobes on intakes,I think high vacuum/no burning was sucking oil in bad...extreme case maybe, as it would barely run until repaired, but if only one cyl on a bigger v-8, the power loss might not be felt. If you do find a wet plug, pull that valve cover, unhook coil, bump starter over to see if rockers moving roughly same amounts.