The only thing that would lag a game would be massive amount of units and sprites on the map doing actions, such as in this map as time progresses:
http://www.staredit.net/index.php?showtopic=33838That map lagged for me even in a replay, and I have a 3 ghz machine, lol.
The worst you can do trigger wise is that if you have a LOT of units spawning with hyper triggers, it is possible your map may crash every now and then. An Uberation 2 Compress and Protect always fixes that problem for me, though.
You could center 250 locations on a unit with hyper triggers and it would probably act exactly the same.