I clean my A390 about every 500 rounds. That means about every third range trip. My AL390, which is my hunting gun gets cleaned at the beginning and end of Dove Season. My other shotguns I clean every time I shoot them, because unfortunately I shoot them so infrequently that I would loose track of when to clean them.
I used to clean every gun every time I shot it, but as I have acquired more of them I found I was spending a lot of time cleaning shotguns, pistols and rifles.
If I am going to clean one I do the complete strip down and clean and lubricate everything.