if you have a decent smithing level... use a armor stand in a POH
99 smith == -50% cost to repair barrows items
90 smith == -45%
80 smith == -40%
70 smith == -35%
60 smith == -30%
50 smith == -25%
40 smith == -20%
30 smith == -15%
20 smith == -10%
10 smith == -5%
I personally just repair it when it breaks, because that is a lot of time to do it.
And you will be doing good since you dont lose stats when it degrades.