When I run nixos-rebuild switch without anything new, it takes like 4s to start printing setting up /etc (so to finish building)… but then it takes 1mn40s just to run restarting sysinit-reactivation.target:
$ time sudo nixos-rebuild switch
warning: Git tree '/etc/nixos' is dirty
building the system configuration...
warning: Git tree '/etc/nixos' is dirty
activating the configuration...
setting up /etc...
reloading user units for leo...
restarting sysinit-reactivation.target
sudo nixos-rebuild switch 0,01s user 0,01s system 0% cpu 1:40,76 total
This is a really long time for not much, which is annoyingly long when we need to apply many changes to our configuration sequentially.
Is it normal? Why is it taking so long? It seems like it would be more efficient to just reboot to apply the changes 
Is there any plan to make this faster somehow?