One thing is for sure, in the tabletop familiars can remain for years if they are not destroyed, so Wizards do not need to spend a spell slot everyday to summon it.
BUT it cost 100 GP per cast.
I would prefer BG3 use the official rule (for the Wizard) : if the player is careful, the familiar lives on after a Long Rest but, if it dies, re-casting cost 100 GP. 100 GP is easy to pay after selling a few random stuff found.
Last edited by Baraz; 09/10/20 03:22 PM.