I don't think it would be a good idea to mix two programs on alternating days. But spending a month or three with one style and then switching to the other is working out wonderfully for me.
I liken it to spending a few weeks doing cardiovascular exercises and then alternating that with strength training. Your body adapts to the regime, and then you change up which stimulates growth.
Generally speaking, people require about 90 days to adjust to a behavior; that's why many substance abuse programs go 3 months.
Seems to me that going 90 days and then changing up would be beneficial. It's working great for me, anyway.