I just cleaned my thunder beast can for the first time. It's a fully sealed unit. I followed the directions on cleaning and it worked but it wasn't necessary having just 400 rounds through it. I'd suggest weighing it when new/clean, and when it gets 1 oz heavier, follow the manufacturer's cleaning instructions. Even though I'd be willing to bet most, if not all, people wouldn't have an issue if you never clean (have read some stories), I personally wouldn't wait much longer than that, because it's easy to do and keeps it running as intended.