I've done it for the whole month on my RX480 twice already. With a proper voltage curve, it doesn't really pull much more juice at stock frequency than a GTX1060.
I've been wanting to try to play around with frequency tuning to see how much ppd you lose per MHz (ie for crypto you can really downclock your GPU with little/no hit on hashrate), but the rewards in F@H seem too inconsistent for anything more granular than ~20% adjustments.
....that and because folding for Frankie takes away the ability to track JUST my stats.
Main: i5-3570K, ASRock Z77 Pro4-M, MSI RX480 8G, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod