Within my apps I often enable/disable menu entries and do make them visible from onPrepareOptionsMenu.
Today I started to add the android:showAsAction menu attribute
I am not sure you have seen it already, but if you use the actionbar extensively, and plan on supporting lower API's (>8), take a look at the actionBarSherlock library. It will make it so you do not have to section your actionBar code for lower and Higher API's, and then you can just run:
runOnUiThread(new Runnable(){
@Override
public void run(){
supportInvalidateOptionsMenu();
}
});