Currently one a level I of mine has 100 objects even, and quite a few backdrop objects (including 3 system backdrop objects). All are divided among 4 layers. Of course, there is lag involved.
Is there any way/method to further decrease lag besides maximizing the compression levels? It doesn't seem to do much at all.
Destroy objects outside of the viewable frame.
Make objects outside of the viewable frame inactive.
Consolidate particles effects.
Deactivate unused groups in the event editor.
Lower the graphics quality.
Deactivate chunks of coding to see if its a programming error causing the lag.
Lower the number of colours.
It depends on what those objects are doing. In my current projects I get between 300-2600 objects at 60fps with no lag at all (in HWA at least). It's aaaawl about the optimisation.