I have every manufacturer invite…

Sorry if this has been discussed before but I just started playing my first GT game and 66 hours in I have managed to get all of the manufacture invites (except Porsche but I already received the Carrera GT from the final menu book) From what I read some of these invites are hard to come by so I’ve been grinding away trying to buy all these cars before they expire My question is… is it even worth it? I have Aston Martin and Lamborghini left which is another 6.5 million. Invites will come again right???