This depends on the Build ID of MyEclipse (Window > Prefs > MyEclipse).
If you are running 3.8.1+ then the major memory leaks were fixed, but we are still doing a heck of alot of tuning.
Also unless you specified memory arguments for Eclipse, you will likely run out of memory during a normal heavy coding session, especially if you include MyEclipse which is ~130 plugins. We would encourage you to add something like:
-vmargs -Xmx256m
to your shortcut used to start Eclipse.