I am a long time (six years) user of 30/1 bimix. My usual routine includes 30 minutes of stationary bike riding, inject .15 bimix, take a shower...play. The bike ride might or might not help, but it is mostly to keep me occupied while my wife makes herself more beautiful. lol
I have always had excellent success, better if really encouraged. My erections have always been usable for several hours, but relax almost immediately if left unattended. Early on I was concerned that I remained moderately hard too long, but my uro tells me not to worry if they are not super hard for a long time.
Yes, erections are harder and longer lasting when I am upright. Since nothing else works for me, I am glad I have such predictable success with bimix.