Basically, I'll probably be doing an IDC (and therefore EFRI) within the next 12 months anyway, I think, so if it only needs to be renewed before my PADI renewal is due then I'll have got the EFRI by then anyway, if it needs to be renewed on the dot of 24 months after I passed it, then I may go ahead and just do EFRI now anyway.
A valid, in-date, EFR (or equivalent) cert is a prerequisite for both the EFRI course and IDC...