My comments reflect your situation on a permanent site. If travelling I wouldn't brace them. In your current situation do you need to support your slides? No. But could you? Certainly, particularly if the months you use it are continuous. I've never bought the argument that slides shouldn't be supported because a sudden shift or settle will cause Armageddon. If that happens, you did a crappy job blocking the unit on a permanent site. Our Cherokee 39RL is about the same frame and size and weight as your Puma with 3 slides, the shortest 5 1/2 feet, one just over 12 feet and the longest 14 and a half. We use it full time in summer and also visit a few times a week in winter and we support our slides which are left out permanently. In fact, each slide has a set of adjustable bolts for snugging up against a block/jack. The trailer is blocked on 6 piers consisting of a gravel/limestone base, extra thick patio stone, a cinder block placed the proper way up and wooden blocks at the frame.
We find supporting the slides greatly decreases the amount of movement and shake in the unit when walking around and gives me peace of mind that there is less stress on the slides long term. Are they designed to support themselves? Yes. But I've seen too many older units with saggy slides.