I've been re-tooling the galaxy generation algorithm to account for the existence of the hexgrid. While doing that I've also been testing the amount of memory that a hex grid will consume and finally playing around with different lighting options, etc. in JME3.
I can now generate circular arrays of hexagons over 400 tiles wide and maintain a decent framerate. The picture below is a sample grid that's about 100 tiles wide.
To keep performance acceptable, I've made the tiles all one object. Additionally, as you move away from the tiles they'll disappear. Note that they become a blue "haze" above at some distance away--that haze will be replaced by a gradual fade out as they recede into the distance.
I've estimated that a low density, 3,000 star spiral galaxy will require a circular gird approximately 400 tiles across, so I appear to be ok. I'll try to get some more pictures together (maybe with a star or two) this weekend!