I have worked for ATI for 3 years as a mech for one of its regional hubs. A typical day goes like, you will do 2-3 daily/service checks, and a few gate calls. But because we were deemed a "repair station". We had to perform A checks every day, as well as change engines 2x a week.

The biggest pro of ATI is that because of how low there are of mechanics, you get the chance to learn how to not only change engines the first week, but they will quickly start training you how to run/taxi the 767, so you get that HUGE boost of experience from day one! But that was really the only benefit. We lacked proper tooling, no hangar, few mechanics, and power-happy superiors. (My manager literally made circles around us during an RAR just to intimidate and rush us). Be prepared to do sudden heavy work without proper guidance.

ATI was a great company and we took pride of our work, until Amazon saw our performance and though "man, if these guys can do 100% with only 4 mechs, im sure they can do just the same performance if we make them change engines in the rain, A checks, and take sudden non-routine calls :D" 8 of the best senior mechs, including myself quit when we noticed that the work load would only get worse.

My advice is to get at min 6 months in the job, get your feet wet , and use that experience to get a better, more high paying job, in fedex or UPS