Full length slides

We have a full length slide. Hydraulic. We have had ours 2 years and no problems. That said, and you will certainly hear lots of disagreements, but just consider the following. Have you ever seen a flat bed semi rolling down the interstate while empty? Notice the huge upward bow in the center. The same flat bed loaded is totally flat. Now I don't claim to be an expert but seems like common sense that there is flexing in long spans. Now think about these long MH slides. There has to be some flexing. A friend has a Tiffin 40' MH and although he doesn't have a full slide he pointed out to me where on and off the jacks part of his paint pattern changes. Obvious flexing. I have been told on this forum that Monaco is one of the only MHs that specifically indicates when you should operate your slides. Monaco state in their manual "NEVER OPERATE YOUR SLIDES WHILE ON JACKS. To do so could cause major damage. Open your slides first, then use your leveling jacks". I can accept that concept. Possibly there is enough flexing to damage a full slide. If a sturdy built semi flat bed flexes obviously a cheaper lighter weight MH frame must have some flexing. I follow the directions in the Monaco manual. BTW our slide runs from behind the driver seat to the rear mounted cupboards in the bedroom. So far we really like the open feeling with the large slide. JMHO.