No problem leaving the gun with 2k air or fully aired up. I would not leave it stored cocked with or without a pellet. If your gun is right it should hold for years.
Congrats on first pcp. I'd try to keep it at least 1/2 to 2/3 full when storing it, but if its unregulated any pressure within its fill range should suffice over the 1/2 fill value.
Great choice. My first was a Marauder in .22. Have an Impact now, and still have the Marauder. No intention to sell it. accurate, economical, and adjustable. Great first choice
Keeping it filled reduces strain on the tank as well. Seems backwards, but by keeping it pressurized, stress on the tank is constant. The expansion and contraction actions that can weaken tanks over time doesn't occur nearly as much.