I've got a 9 (arrows) x 7 (arrows) base, so that's 64 squares, if my math's accurate. Costs me $30M to expand. I had every single non-gold Money Building, non-gold Boost Building and Unit Building and I have 12 LTE Buildings. I had room for all of them, but with the next LTE Building coming out after India, unless it was a Water Building (which is unlikely), I wouldn't have room for it without expanding. I can't really justify spending $30M for a $45M +/- Building, so I sold off all of my Money Buildings except for the ones I had to level 10, 12, 24 and 48 hrs Buildings.
So, all I have now are Unit Buildings, Advanced Unit Buildings, Boost Buildings, Supply Depots (5 min-lvl 10), Armorys (30 min-lvl 10), Storage Silos (1 hrs-lvl 10), Oil Derricks (3 hrs-lvl 10), 5 Mine Fields, 5 SAMs, 5 Railguns, all the non-gold 12 hrs Buildings, all the non-gold 24 hrs Buildings, all the 48 hrs Buildings, both Janai Facilities, bothCurragh Engineer Buildings, both Santa Marta Train Stations, both Tatra Outposts, both Queensland Barracks, both Absolute Towers and now both Taj Mahals, with PLENTY of room to build new LTE Buildings.
My goal now is to upgrade all of the remaining Money Buildings to level 10.