It all depends on your duty station and what additional duties you're tasked with at your unit. It's hard to gauge, but I'd argue most days it would be easy to work 12 hours if you're doing your job right. I work at a very high operation tempo unit and I'd say I do 10-12 hours most days. Every now and then there's a random day or series of days that are 14+ hours. Occasionally I'll work only 6-8 hours (Fridays most often), but there's PLENTY to be doing at your own job, let alone performing random taskings from higher and helping coworkers.