A last post about that and if there is no solution or answer, well, forget it, i will do with it.
Just to detail what i have :
My game uses 42 mo (with ejecta, 50 with cocoon, but it's not linked to my pb, ejecta has just a better use of ram) on my devices. 12 are the "base" that you can't get rid of, the rest is what i did, so around 30. My pb is that i'm only using that in my images folder :
7x256 > 1.8 mo (spritesheets)
4x128 > 0.2 mo (spritesheets)
4x512 > 4.2 mo (spritesheets)
2x64 > 0.03 mo
8x8px > like nothing
(if i was good in calculate the use of ram as written by Asley here : scirra.com/blog/112/remember-not-to-waste-your-memory)
I'm doing nothing specific in my code, but i noticed that the more events you have, the more it uses memory too, even if it's not enormous, it's there (i have actually around 300 events in total).
So whatever, it's just to show that my game is optimised on that point, cause it doesn't change the pb : i don't know why i'm using so much ram, and why when i re-use my graphics, or duplicate a scene, the ram increases so much, even if i don't add events.
Ashley : can i send you my project to have a look ? Maybe i'm doing something wrong somewhere or maybe you can see what is not working ?