Sorry for the noobie question but atm i have all the event dragon balls gathered on a lvl 6 character , was planning to keep them till lvl 40 to be sure i can get the transform then , but question that popped to mind was , will the event ones still be usable by the time i get to lvl 40 or they will be unusable after i use the quest dragon balls at lvl 20 ?

they will be fine

Alrighty tyvm , first time i manage to gather them all , now gotta get them all for my gf too then were done :D