When closed, does a substack whose destroyStack is true remains in memory ?

[André.Bisseret]

Hi !

As far as a substack is concerned,
from the Doc (on save, close, destroyStack…)
I understand that :
even if its destroyStack property is set to true,
If I save and close this substack while the main stack remains opened,
then this substack remains in memory.

If this is true, then I understand that it is not judicious to set « 
formatForPrinting » to true for this substack.

So, for a specific « printing stack » I have to use a second main 
stack, instead of a substack.

Am I right ?
Thanks a lot in advance for validating (or invalidating) these claims.

P.S. : by the way, is it a means to check if a closed stack (or 
substack) is still in memory ?

Best regards from Grenoble
André