Think of it like learning to ride a bike or drive a car.

At first, you are all nervous and continue to monitor all your mirrors a lot more often than needed as well as your speedometer, et al. But the more you keep up with the process (drive or dive), the easier it seems. Then it became second nature...

I suggest that once certified, continue to do a lot of long easy dives that you don't to do a lot of multi-task so you could devote all your time to recognizing how your unit is working:

• sound of solenoid firing, or sound of continuous flow of O2 (on mCCR)
• sound of gas swooshing in (with solenoid firing)
• sound of the gurgling to start in your hoses after a certain amount of time
• how long between solenoid firing for different exertion level
• how close is the set-point being kept
• etc and etc

There is no fix duration of time as people are all different.

However, if you do immediately after the course to keep up the momentum, it will be easier. If you take some time off, the first dive back will be a little awkward with no one to supervise to let you know that you are still doing it all correct.

If you have a good instructor and a good foundation, it will be a synch!