I've got to agree with most other posters - cruise 1200's w/ 1 min recovery is a great workout, but pretty similar to a 20 min tempo. It's basically a tempo with short breaks built in to allow you to run a bit faster than normal tempo pace. Alternating tempo one week, cruise intervals the next during a base/build phase sounds like a better plan.
Instead, I'd build in one 'neuro-muscular' effort every one to two weeks - something fast enough to "keep in touch with" your speed, and to increase efficiency, but at a low enough volume and with enough rest to not generate much cumulative fatigue. I like 3x(4x200) at faster than 5k pace with 400 walk/jog recovery, 5 min walk/jog between sets, or 3x4(15-20 sec. hills) structured the same way. You can do this on pretty small hills - I've done this on highway overpasses, indoor parking garage ramps, etc.
The other thing I like to build in is what McMillan calls "fast-finish long runs," pushing the last 1/3 to 1/5 of your longest run of the week. The pace might not even get down to true tempo pace, and if it does, it would only be for the last half mile or so. It's a pretty tough workout mentally and physically, but for me at least leaves me feeling pretty good the next day. If you want to progress to getting some more faster running into your week, that could be a good way to do it.