I feel like limiting long rests on harder difficulties should be a thing, but not at all levels of play.
As many have noted, the DM decides how viable resting is for the party in a pnp, but there is no DM here. Plus, the game can't take into consideration the party composition, which is something I as a DM always do.
As it stands a martial party might not need to long rest for ages, but a full caster one will need one quite often. How do you balance that in the game - I am not sure.