I think they need to start considering now the difference between Pfizer and Moderna.

Because Moderna had a higher initial dose (resulting in more side effects), it's looking like it will last longer. It would make more sense to give a third dose to Pfizer recipients and wait a bit with Moderna.

(I am talking about healthy adults here. The considerations are different with immunocompromised and with older people who may need a third shot sooner).