It's a personal choice. We leave ours in when not in use. Our Motorhome had 2 slides. When they were in, the camper was still completely usable. Our current Destination Trailer is not very usable with all 4 slides in. The bunkhouse is completely inaccessible with both slides closed. There is just enough room to get to the slide controls. We leave the trailer on site all year round, but will close the slides when we leave at the end of the season. Even if it were parked at the house, we'd probably leave them closed when not in use.
That's our choice, others choose differently. There is no right or wrong.
-Michael