The silo seems to be the easiest to upgrade but the number of crops is relatively static. Yes we got 2 new crops but it has been awhile since that happened , while new barn products increase much more rapidly. Plus the need to expand the barn is complicated by the fact that all the expansion materials sit in the barn! If they were to sit in a separated shed, it would be much different. I'd like to suggest that silo expansion material sit in the silo but that could be a real mess. it would be literally like looking for needles (nails/screws) in a haystack

