During those stints I like Jim Wendler's "Effective Training for Busy Men", the A/B routine.
Of course, you alternate between the two workouts through the week, but you can create a third if you like. The workouts focus on two compound lifts and assistance work, and usually take about 45 minutes to complete.
You can shave off time by limiting your work sets to maybe two or three, and by watching rest periods. The duration includes warm-up sets, but because the CNS is already primed when you get to it, the second exercise will require fewer warm-up sets than the first. But really, it is assistance work that can eat up time. So try to find a balance when programming.
I also save time by moving recovery work to an "off" day where it's not a big deal to set aside ten or fifteen minutes. Stretching and soft tissue work is easily done at home, and I never felt it hurt my training when I didn't do it on the actual day I lifted.
One drawback is you're repeatedly training the same movement patterns. An occasional week off is good, so are variations of movements from one mesocycle to another. (E.g., switching from back squats to front squats.)