the default of maya's undo steps (queue size) is set to 50. this may be just enough for you, but you can also set it to infinite. the upside is obvious, the green soylent is: it may decrease maya's general performance during your session. but just type in "flushUndo" into the mel script line of the gui and free up memory whenever you're happy with your results. so if you get your hands a little bit dirty, you can gain a lot.
More
CEO