depends on the dose you are trying to run,, but yes twice a week is better every 5 days is a pretty good low start cycle,,,, want to up dose run every 4 days more every 3 days ect....
once or twice if fine. Depends on how much your taking too. If your taking 500mg a week you'll want to pin 2x. If your doing a low dose cycle of say 250mg 1x is fine