good question .... If I play a star vampire, most of the time I put 5 copies in it because it turns out to be necessary - )
if you gonna put them both 4 times in your crypt, i think you gonna have a bad crypt draw too often. Maybe a ratio of 5 / 3 and and alternative for the last vampire if there is ... You can add anarch convert or tupdog in crypt to cycle it or might put some cards in your deck like effective management, recruitment, info highway, wider view ... or clan/skill specific cards: summon the serpent, soul scan, stranger among us, mesu bedshet, .... hope I mentioned something you didn't think of ...
My "Marilutz" deck works pretty well with 4 Maris and 4 Lutz. Of course, there is the odd game when one of the two is missing and the deck is not optimal... but it still works with the "replacements" Rachel Brandywine and Quentin King.
Emiliano "Sans Terre" - Wandering Player - Prince of Brussels
In my Lutz Anarch Revolt deck I use 4 Lutz, 4 AC and 4 Lutz-backup or enhancers (Cybele, Aksinya, Nana, ...)
Not having Lutz in the opening crypt sucks, but having only Lutz in the opening crypt sucks even more.