The closest trees in my backyard are 25 ft. apart. Not only do I mount the tree straps high on the tree (9 or 10 ft.), I also use continuous loops to extend my six ft. whoopies. At 25 ft. distance, you need to add some length to have any whoopie adjustability.
I used to make 10 ft. whoopies just because I wanted to be prepared to hang between trees 25 ft. apart, but on the trail I have never hung at that distance. That's why I use the continuous loops to extend the whoopies. I carry a couple in my pack in case, but I've never had to use them on the trail, just in my backyard.