I am running 32gigs of RAM and I can manage to fill it. I do not often do.
But I also maintain RAM swiftly if I worry about getting close to spills:
I use autokey to speed this process up.
A partition is needed for hibernate due to how hibernate shuts things down. A swap file may not be reachable early on during init, whereas the partition is read easily and quickly, early on by UUID.
Since it must be loaded that early - it must be on its own partition.
Whereas without Hibernate, a swap File is fine since it is a complete cold start, with RAM emptied and at its lowest state.