I'm not a SRAM user. But some of their 12 speed chains don't work on 11 speed rears. I didn't see that you said what rear that bike has on it.

All chains for bikes today and for most of the past, have a 1/2 inch pitch chain. On some SRAM and maybe even some other brands of 12 speed drivetrains, it was the roller size that changed. Not the pitch. And the external width has periodically changed also.

So when you say the pitch of your old chain was longer, I assume you mean it was worn and maybe a 1/6 inch longer at what should have been the pin or other measuring reference the origin of your scale was on when checking if it was longer than 12 inches.

Chains shouldn't wear out too fast. But I don't know what 3 hours a week equates to in mileage. I have a 11 speed chain with over 8000 miles that many here are in disbelief of .

2000 miles of chain life might be reasonable if you tend to pedal a slow cadence and muscle the bike up hill in a hard gear instead of shifting to a ridiculously easy gear and pedaling up that hill at 90 - 100 cadence rpm. IMO

You also might make certain that all your drivetrain is running compatible stuff. And since you are having issue, if no other member here gives you any solution, then go back to a chain and cassette from the maker of your chain ring. And make certain they are all shown as compatible. Not all are.