Current Startup Doing Great.... Will Working On Side Project Slow Us Down?

I cofounded an awesome startup and things are moving along great. We got accepted into an incubator, and ended up leaving with a viable idea, customers, and initial traction. Now our company is doing pretty well, we just hired our first employee, pretty much bootstrapped profitable, and I cant really complain. 80% of our time is focused on scaling our customer base, we are still in the "trough of sorrow" phase but our "wiggles of false hope" are keeping us alive.

The problem is I have a couple other ideas that I keep getting alot of great validation from. I set up a launchrock page, and have thrown around around $100 in advertising and the page is getting alot of signups.

So I'm wondering should I build out an MVP with some of my free time or forsake this new idea since I'm so stretched for time. We are doing at least 11+ hour days on the weekdays for our current startup so I'm pretty busy as it is, but new traction on a new idea is hard to turn away from. And as a developer, I love building things so a new project definitely seems more interesting.

So where does the community stand an issue like this? Keep 100% focused on the startup that works vs. Building something else new that could suck away time, but that I have a good "gut feeling" about?