Hey Lars.
Because it is controlled via DMX values I would go for 256 slots.
This is the way media servers organize their media librarys.
For
me this would be most logical way to do it.
It is not that I want to have 256 scene changes in one play but a mean to organize/name my scene changes in a way that follows the numbering of acts / scenes in the performance.
I am sorry that I can not give you a number of scenes I actual would need, because I can not predigt what the needs of future projekts will be. ;-)
Best regards,
Alexander