I play my original 1971 D-28 and the sound continues to improve with age. I play mainly folk music, country and the blues and use John Pearse accoustic 650's. They are Phosphor Bronze Wound Bluegrass strings and seldom disappoint.
The only time I have a tuning problem is if we're playing an outside gig on a humid day. That's tough for most all guitars.
In the meantime, keep on pickin'......it 'll keep you young.

Best regards to all.