Last May I ran from BLT to the Poly and back - map below. It was 3.1 miles though I only ran to the beginning of the Poly and not all the way to TTC. You could certainly add more distance by looping around any of the resorts' paths, and extending out to TTC.
A few things to be aware of, however:
1. the normal path along the water between GF and Poly is currently closed while they build a new Poly building. There's a detoured path out to the road where you're still on sidewalks but it's less scenic and less straight forward (parking lots, construction walls, and a road).
2. as others have said, you'll have to pass through MK security in both directions which is easy enough to just walk through the scanners
3. early morning, the pathway between GF and MK is actually blocked off at a point (the second picture is a run during marathon weekend where I had to turn around at the drawbridge gate). The arrow points to where the bridge is, though I did a second loop and turned at the security checkpoint (which is why the track extends).