Will payout rates be the same for some time?
For some time, but I'm afraid not for the long time. The current efficiency of the campaign is very low.
This sort of campaign likely isn't suited for your business with such a low commission rate (and mixing your coins is kind of a niche still). I think you'd benefit from advertising but on a smaller scale. I'd suggest changing up your campaign to a fixed rate and setting a budget per month. See the Luckybit and Bitstars campaigns for examples.