Red mites survival? Bedding disposal

Good day fellow chicken enthusiasts.

Last year we had a nasty infestation of red mites in our coop.

My wife and I emptied all bedding and bagged it in industrial garbage bags. Cleaned the coop and ensured there was no further issue before bringing the girls back. We've had no issues since.

The bags of bedding were left outdoors in the PNW since July / August. And we're sealed so they were subjected to high temperatures 28-30c And then down as low as -7 to -8c for a couple weeks.

We'd really like to put the bedding in our garden but I'll be damned if I want to risk another infection with those little bastards...

Whats the advice?

Cheers