I'll start it off with Neil Young's 'Psychedelic Pill.' (2012)
I'd rate it an A-minus and Neil was 66 when it came out.
Of course, he used to churn out albums that good or better on a regular basis in the '70s and this was his only one (IMO) that good for five years in either direction, but that's probably because he's really old and just not that good any more. Maybe he was so jacked because of his Pono launch that he was inspired...
To pick from a different decade of initial success, I'd also give a (weak) A-minus to Sonic Youth's The Eternal (2009). The band was in their early 50s when this came out. I found it to be a slight improvement over both Sonic Nurse and Rather Ripped, but the trio of albums nevertheless were examples of how the band (eventually, after 20+ years of innovation) began to re-tread their music somewhat. IMO, The Eternal was the most successful of those three albums at being that kind of album. I guess I guess it more or less proves my rule instead of being an exception, since the band hung it up soon after releasing it, not interested in becoming a nostalgia act for Gen-Xers.