You are right. I would not do this, but if user cannot understand the situation maybe he will see how I am feeling when he calls my site a ponzi, when it is not a ponzi.

And yes, it's planned to work faster, but DoubleBot is still under construction and I am not promoting it for the current moment.
There are couple of reasons: 1. I have no time now. (Will have some time later).
2. The site is still young and too much people are calling that "ponzi".

After making some changes I will began promote it.

The grow of your percents is not constant. So, you can spend 1 months for 7%, 2 months for 1% and 10 days for 92%

The previous (and still current) system counted payments as:
0.1 btc will be doubled for X days. 0.2 btc = 0.1 + 0.1 btc and will be doubled for x2 days.
But as I can see this logic does not fit to real users expectations. And some of them are mad )