Flying isn't the hard part. It's the procedures and SOP's that get rusty. I've been grounded several times for 2-4 months in the airline business. With experience it comes back quickly. Obviously you're slightly rusty but for normal ops it's fairly straight forward.
Coworker and I were both grounded for 12 months from flying an attack aircraft. I was grounded first, he followed after I returned to flying, so he asked me what it was like. I told him it would it come back much quicker than he realized. I flew with him on his first return flight, on a low level flight, to the bombing range. Returning to base I asked him "so, what do you think?" "SOSDD." There are some restrictions when you come back to flying, like the minimum low level altitude was raised to 500', no low level pop-up bombing runs, etc, because your brain does process slightly slower and the maximum of 5 seconds wings level on the bomb dive goes by quickly (!).