HDDs are made for this sort of thing, I've formatted a single hard drive like @someone somewhere said like 50 odd times. RMA means: Return merchandise authorization, basically if it fails and it's under warrenty or if it fails and they cover it then you can send it back and the company send you a new one.
Seagate is a very good make, there is no limit really and it's unlikely a seagate HDD will fail from formats. They are very good.