Interesting question.
As someone who is working full-time and working on 2 start-ups (one with far more commitment) I know what it is to take one too much as an entrepreneur.
The first thought is a warning! Burnout! If you choose to go full-time and a startup you're going to hit a wall. Naturally if you do more than one startup you just hit it faster...
So the issue is commitment. My advise would be to divide your week into blocks of commitment for each project. In my case Mon,Wed,Fri,Sun using 4 hour blocks per dsy for startup A. Tues, Thurs of 4 hour blocks on startup B (Saturday is a much needed recovery day, normally resulting in a much deserved hangover).
Another consideration is how you work...
For example I am an 80/80 person. I work 80% and play 80%, the important part is that i'm never 100% at one time so have that buffer to avoid burnout... you have to find a balance between the minimum required effort to have a successful company and your own personal space (even work-a-holics sleep, generally on the keyboard)
As you have experience with startups i'm surprised you've so easily embraced another two projects. However that intimates that you know how to divide you time between them... It would be interesting to see a blog post from you in 6 months to discover if you were able manage both and how the progression/success of each respectively influenced your commitment in them.