It depends on the total length of the string. The length they show on the package is not always the real length. For example, a set of YPTS says it's only 39 ft, this is not enough for me to string the mains of 2 rackets, but after measuring this set of strings myself, I noticed the real length was at least 41 ft. This is more than enough to string the mains of 2 rackets.
But if you're strings are really 40 ft, and you need to string the mains of two oversized rackets, It's going to be a very difficult story.