On the previous version the swap file never really increased, even with 4GB RAM. On version 16, what I'm finding is the swap is gradually increasing and the performance is decreasing. Before I upgraded I upgraded the unit to 8GB.
I find I have re reboot the unit prob every two weeks to clear the swap and improve performance again. I've also had some Ring devices that stop working. Reboot fixes it.
ATM TBH I'm looking to swap out for an alternate NGFW.