How long until we get 2 more grails at least?

Because of the Da Vinci event, i has to raise a budget rider to farm quest, so i used Blackbeard and realised i really liked him. But in the middle of the event i got Jalter and hurried to max ascend her and even grailed her, so i don’t have many grails now.

Long short story, i’ve already used 2 grails on robin hood (my fav servant) and 2 on Jalter (best servant i’ll ever get) having left only 3 grails. Now i’m conflicted bc i want to grail robin to lvl 90 as i’m close to his bond ce, but i also want Jalter lvl 100 or Blackbeard lvl 80, so i wanted to know when do we’ll get more grails. it’s just that i’m afraid i’ll regret it later if i choose one