Ok guys

I would not have a TT without a dust cover when not in use. It's a great place to place a tray of house plants on, while keeping everything clean, especially the refined moving parts of the tonearm.

Open or off when playing. If you believe in microphonics, open, let em go.

Hinged dust covers up while playing? Keep a bubble level on the deck. Does it change when the dust cover is on-up? surprisingly a few I had did not effect level. 

If effects level, you can remove the hinges and just put it on whenever.

Seriously, we bought a very nice unit for audio equipment and I told Donna she could have the top glass shelf , table height, for plants. Well, eventually, to get some stuff on that shelf, and keep my word, I painted 2 cafeteria trays, big felt strips on the bottom, and they actually look better higher up. I trust her watering skills. Just move the tray off the TT to the top of the Reel to Reel Dust cover, play on.

Mijo
It would be nice if for once you could just accept the fact that your opinions are going to differ from other members.
Nobody is arguing that what you state in your system is what you hear and great for you.
However maybe you could just accept that it is in fact just your opinion and not try to foist that off to everybody else here as being gospel.
It works for you and that's wonderful, apparently it does not work for a lot of other members myself included and that should also be wonderful, not an area of contention. 

Richopp, I did not endorse Kenny G. I included him in a list of things about which people disagree vehemently. If you must know, I regard his music as a particularly brutal form of torture.

Mijo, you have an inordinate dust phobia. I am glad your dust cover ameliorates your anxiety. I however will never ever even consider using a dust cover whilst playing an LP. I clean my LPs with the Audioquest carbon fiber grounded brush just before each play and I clean my stylus with Magic Eraser before each side. LPs that don’t have groove damage from previous owners play silently in both of my systems on any of my 5 turntables. I do also clean any used LPs I buy on an VPI HW17. If your sota sounds better with cover down, that’s a good reason to use it. It’s fine with me, even if you like Kenny G.

If the table has a hinged dustcover, it should be down. Look, it's your table...do what you want! I am sure that the reason that manufacturers included a hinged dustcover was so that it could be closed while in use.  

+1 to @audioman58 for asking what turntable the OP is using.

If the OP’s system description is up to date he is using a ProJect Debut Carbon DC, which is a non-suspended belt drive table weighing about 12 pounds and costing ca. $400 including an Ortofon 2M Red cartridge. Certainly a very different animal than the SOTA tables which are the only ones to which my earlier comments pertain.

Regards,
-- Al