You can give the armor to the guards in Dragonsreach, and it'll keep. I don't know about any other guards, though. I doubt they'll wear it, though.
I know it keeps because I've given all 4 (two in the morning shift, and two in the evening shift) daedric arrows and ebony bows and they're still there after 13 levels.
Without their archery practice, I wouldn't have 300+ daedric arrows, that's for sure.

Edit for censored typo :embarrassed: