I think it's simple, if you NEED then you procure from the closest source. Kind of like our local procurement.
One of the guys that was 101st during Arnhem said they came back from Holland and turned in all their gear and clothing, was all completely worn out from the 70 odd days of wear and combat. Then while they had nothing the Bastogne surprise came along. It's a matter of what you're doing. You can have a piece of canvas for years if it doesn't see much use. These are right where they get worn so if you're in the field for extended periods it would be consumed. If there's any holes or serious wear it's considered unserviceable.