I'm a little busy right now but the short answer is: You can never have too much memory.
It isn't as much a "format" question but rather that the whole ATC system is going RNP which translate into more complicated and thus memory hungry procedures.
Every day ATC procedure designers are developing new RNP / RNAV based procedures to be loaded on top of the conventional procedure. In the case of Honeywell you cannot get rid of the procedures you are not using, as Honeywell insists on loading all "standard data" - even including the ones you are not allowed to fly.
Every AIRAC-cycle update you get contains both the current data and the next data. When a new cycle carries a lot of changes, you will have to load these on top of the current data. This could easily result in a demand from Honeywell that you remove some destinations and their associated procedures to make space.
Rgds.
dusk2dawn
[desperately managing nav-data for a fleet with Honeywell Non-One-Mega FMCs]