5-10% per month is absolutely unsustainable unless something fraudulent is happening. I always have asked myself, why would this person need other people's money if they are making 60-120% per year. Basically doubling to tripling their money every year? Even starting with 100,000 at 60% per year would net you 1.2 BILLION dollars after just 20 years. No way they are doing this out of the kindness of their hearts, totally a scam. Get the money out as much as they can, but be ready to give back all their gains as it's quite possible they'll have to repay the others after this gets prosecuted.

Typical stock market returns are 7-10% per year, not per month.