I've been at 700 since level 39/40 (before cocoa and coffee -- can't remember what level you start getting those) and I average at 550. Mostly because I am always looking for cheap fruits from the paper. Only once did I go over, lots of 110 coin apples for some reason that time, but after getting rid of a few wheat, I was ok. Then a visitor came and of course asked for lots of apples which I gave (I make money quicker selling apples this way than in stall) and I was at 550 again.
Like you I get a lot of silo material. I just looked and even without trying I am close to half way again (and I keep steeling them in stall unadvertised). After I get my barn built up I'll go back to upgrading the silo for kicks and giggles but for now, it's fine.
GC: ea_sweetface. Scroll over to level 43 to find me today