Flircat
I was lucky in that respect that I got a command at age 28. I am now almost 50. I was in a similar situation were I could go as F/O on a bigger a/c or Cpt 737. I took the latter. I had friends that went for the F/O position on the BIG A/C. They were /F/O for 10 years longer then me. The situation may not turn out to be the same for you, but if you have 1000-1500 hrs in command on the A320 you are in a good situation to bid for cpt positions on A330 in many companys.
Good luck with your decision