Well I usually play small maps so I can finish things faster but I now started playing standard games and will move to large later on,
If you are serios about limiting the time consumed by Civ3, than you should not move to large maps. Even standard maps are quite big and time consuming, they should be interpreted as the exception, not the rule(small). I effectively ignore large and huge and think
tiny(60x60/2=1800 tiles) = small
small(80x80/2=3200 tiles) = standard
standard(100x100/2=5000 tiles) = large
large(130x130/2=8450 tiles) = don't even think about it
huge(160x160/2=12800 tiles) = maybe i find time for this after i am dead
The smaller a map the faster a proper point can be found for saving the game and possibly stop playing for now. At large maps it takes very long to get a good idea of where you left of. Large maps might be fun for pure AI vs. AI games, but the human mind is not really made for this.