The easy answer is to pull them in. ZERO risk other than more use = more wear. The more frequently you slide em in and out the more likely you are to experience mechanical failure. Thats just the facts.
The tricky answer depends on if yer smart enough to set it up so that a flat won't create undo stress on the slideout. It's not rocket science, but theres lots of folks out there who are anxious about doing anything outside the boundaries of what the "experts" say. NEWS FLASH...the experts say what they do because they want to limit liability not because it's actually a best practice. If the experts said to support the slideout and little Mr. pay someone to do everything for him comes along and decides to jack it up instead of support it or supports it without the leveling jacks down...voila...instant lawsuit once a tire goes flat.
So, for those that arent afraid to think for themselves and have reasonable mechanical kowledge, supporting a slide out is a no brainer. If you only trust the "experts" and get anxious about thinking outside the box, leave em in. The worst that can happen is premature wear on the motor brushes, higher risk of puncturing the seal, battery drain, binding, increased maintenance, etc...
If you don't have the blocks/tools to set up your RV so the jacks wont sink, then keep em in.