After every 3-4 range sessions, so about 1000 rounds for handguns and 300 rounds for rifles unless I'm taking them to a match.
I'll also clean my gun if it has more than 200 rounds down the pipe and I'm carrying it.
I think that revolvers chambered for shotgun shells are just a marketing gimmick. If you want something for serious use, actual revolvers are more size efficient.
People call Corvettes 'Vettes,' Bimmers 'Beemers,' Glocks 'Gats,' Browning M2 'Ma Deuce,' Krinkovs 'Krinks,' Remington 700 'R700,' and the list goes on. Travis Haley's marketing team probably felt like he could differentiate himself from the list of AK trainers by coming up with a unique name...
WHATEVER YOU DO, DO NOT FIRE 9x18 OUT OF A 9x19!
The bullet diameter of a 9x18 is 0.363 and the bullet diameter of a 9x19 is a 0.356. It's stupidity like this that leads to people hurting themselves and ending up on the news.
Unless you're getting an amazing deal on it and the Colt upper is truly all Colt, I wouldn't want that type of setup for my first AR.
A telescopic stock and a flat top upper will give you many more options on how you configure the rifle.