Unless you're going to be in it a lot, there's no reason to leave the slide out.
That leaves the seals exposed to weather and greater possibility of water intrusion.
The trailer will be better sealed by leaving the slide in.
Dan-Retired California Firefighter/EMT
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity