Well I take it for anti aging, and yes, I do believe there is a strong beneficial anti aging effect if taken in low doses. The TRIIM and TRIIM X (which is still ongoing) studies have shown some pretty awesome benefits so I am a believer. Watch anything from Greg Fahy on youtube if you don't believe me. I also take DHEA, Zinc, & Vitamin D (but not metformin) that they use in the trials.
That being said, I take 1iu before bed.
In my crazy days, I experimented with as much as a whole vial of riptropin (which was about 15iu) per day at one point. I was using 5iu most of the time for those years though.