One of my snakes probably arrived with a mite or two that got onto the shipment box, because the mites didn't show up until a whole month (or a month and a half?) after I had the snake. And they were a ton of babies at that point, plus only two or three adults.
So quarantining is necessary! Things can linger and not show up for an entire month or more.
Anyway, it's not possible to get snake mites just from bringing your snake outdoors, because snake mites are not native to North America. They're only circulating within the reptile trade or new imports, so you can only get them from an infected captive snake at a show, shop, etc. or touching one and accidentally bringing them home.
Finding them on feeders would also be very rare, because snake mites don't live on feeders... The only way would be if the feeder recently came in direct contact with an infected snake.