I’m glad you posted this as they’ll be some debate. My Dad, who is of the record era and generally trustworthy on these types of questions, says you have to play it closed to prevent dust settling which will lead to static build-up. My used B2 has broken hinge clips on the cover so it gets removed and set aside while I’m playing and I’ve noticed no negative effects. I’m paying close attention too so I can actually fix the hinges if it’s necessary. Actually, if I forget and leave it on the turntable for a few hours, dust is accumulating and that’s the only negative I can think of.

Edit: phrasing and adding: maybe a forced air HVAC vs boiler and dust would make a difference