Yes they've been legit so far. It's the largest program of it's type. What it often means though when programs come up with new high paying plans, it means they want to suck in as many people as they can before pulling out.
You'll get your money back after 2 months, for a program that lasted more than 2 years, seems unlikely it will collapse now. I might invest myself.
How do you know the program has lasted 2 years? It seems impossible for a 700% return every 6 months to remain unknown for 2 years.
My bet is that the scammers bought an old domain (if that is where you get the 2 years), just like a scammer can buy an old bitcointalk account.
It's not unknown it's the most notorious hyip, no1 on hyip.com
You can look at it this way, as long as it's more profitable for them to pay you than to scam you, then will continue to do so. If they happen to be lucky enough or skilled enough to turn a good profit with your cash, then, site will function. You probably have not heard of forexking either, they'r ranked 15 000 on alexa, people make 50k withdrawals, according to stats on the site.
In the last 2 weeks very big sites went down (pokeram and atlantinv), very much "solid", long-standing sites, poof gone.
About your other question, there are forums & monitors that check the health status every day so you can be pretty sure the site has existed and payed for as long as it has.
Of course this is a scam
Ample warning has been placed about this site and many others.
Also never listen to the pool/awful advice of board members such as, example above.
Only scambags looking to profit off of you and the theft of others.
, and plan 1770 1 year no withdraw 1k =10k 
