I would recommend a GS on turn 72 and plant him as an Academy. This will likely generate more over the course of the game than a bulb at the end of the game, not to mention that technologies will come sooner throughout the game creating a snowball effect. It is not quite as powerful as Babylon who can get a GS for an Academy with writing by about turn 16, but it makes a huge impact...especially on the early game.Mayan Long-count forces one to put great people to good use!!
Yeah, I managed to research Theology pretty easily by turn 63 on emperor so got these long count GP @:
72, 86, 101,117,133,152,183, 234
The first two took Admiral and General as suggested...
Then it was Engineer (wonder), Merchant (CS Ally and $$ for settler), Great Artist (to extend Golden Age), Scientist (saving), Prophet (extra faith points).
I generally plant GS up until the Industrial/Modern Era. Somewhere between Public Schools and Research labs, I start saving them for bulbing later.