Well, the hashrate you rent now won't be worth much later on. I think it's quite worthless in about a year, as there are way more efficient ASICs on the market by then and the difficulty of the Bitcoin has increased a lot again. 

An exception to this is that if you have rented a lot of hashrate. Sure, you will still get an income in 1-2 years, but it won't be much.  However, the target is to ROI before that time .  I think it's a bit of a marketing strategy to promote 5 years of mining (allthough I believe they keep your hashrate running).