I've injected sust 2xwk 3xwk and 4xwk and any of these three ways will produce good results. Now I have no scientific expiation for this, but I just feel better injecting 4x wk. The whole process just seems to work better.
I know a few guys who only inject sust every 7-10 days and they do ok, but I believe they could do better with more frequent pinning, 3x wk at minimum just makes good sense to me. Injecting infrequently, especially only every 7-10 days just goes against the time release properties of sust.
I even no one guy who only injects every 15 days. He claims because of the deconate this is all he needs, and that anything less then every 15 days is over-kill. I've tried to convince him otherwise, but he is just too stubborn. Note: don't be this guy, this is in regards to all advice you receive concerning AAS. When you receive advice when you research any AAS, when the evidence is there that you are not doing things correctly, take notice and make the proper changes. Don't base your decisions on your own stubborn ignorance.