My bet: less than 6 months
I've seeing some hyip monitors and I was shocked to see some of these things are running for more than 1000 days!! That's 3 years!
21st of Sept will be the judgement day. if they'll pay 4.5 BTC to the winners of referral contest (https://bitcointalk.org/index.php?topic=762942.20), then the chance are higher that they will stay at least for 2 months as they need to recover their campaign costs.
The only thing is (a hint he will not payout the 4.5BTC) is that he doesn't seem to want to use escrow which is a major no-no if you want advertisers.