M103 170kmiles, 1quart oil /600miles, stem seals only or valve job?

[Bruno_300TE]

Hi everybody
My 300TE from 1992 burns too much oil (about 1 quart in 600 miles), also there is plenty of gray smoke upon hard acceleration (eg when resuming speed after toll stations). I know the manual says up to 1 quart in 600 miles is ok, but my bet is that's because of the liability issue.
PO had the headgasket done and valve stem seals at 100 kmiles. I plan to keep the car "forever". Engine starts well all the time (max cranking 1 sec), mileage is good, runs a bit rough at high RPMs, power seems good too.
I am tempted to have a valve job done (seats, valve guides) instead of just replacing the stem seals.
What is the board's opinion, is this foolish overkill at this mileage or a reasonable job at this mileage for a keeper?
Your opinion is welcome!
Thanks, Bruno