Map optimizations wont eactly fix anything. In actuallity I've heard more complaints about it CREATING lag rather then REMOVING it. So I'd reccomend against it.
Lots of triggers will not cause lag. However, certain kinds of triggers will...or will al least eventaully lead to lag f the game continues long enouph. Triggers that have reference to points, such a units being ordered to areas in a region, or units being created at a point, or special effects and sounds being created at a positions of a unit....all those "points" are still stored even after the trigger action has run or the unit killed. After a long game, all those add up, and will begin to create lag. So in short, constantly looping triggers with such point references will eventually lead to lag.
-VGsatomi