There are two things here.. breaking even in btc.. breaking even in fiat.. And then there is the time frame. I am more concerned with breaking even in btc, as you rightly put. However, the time frame I choose is a long one. I sat down and calculated the whole thing in reverse. That is, i started actually from how many btc I want to have at the end of 2 years, with the investment I am putting in.
I calculated compounding with a 50 percent difficulty increase in mining and a 50 percent price decrease in BTC. I figured out that if I compound for a year, on a daily basis, with considerable starting investment, I could quite easily break even at the end of second year. I calculated for monthly compounding, and figured that out. That gave me a break even in fiat that I am comfortable with.
Then I looked at the price of the contracts, and waited for the markets to rise to the level where i could get the TH/s I wanted for the BTC I put in for it to work.
So far, I am ahead of my calculations by about 150% per day, even with the China FUD (meaning, my daily rewards are 150 percent right now of what they need to be for me to break even). So, so far so good! Fingers crossed. :) Ofcourse, I am not doing any affiliates thing. I spread my TH/s between genesis and hashflare evenly. And even if one of them changes their contracts, like hashflare did, I am still quite well above the water so to speak.
I think the key is to calculate for the worst and to compound. As long as genesis is up by oct 1st and I get to compound, I should be fine.