That makes no sense to me. The only deadline for the training Flight is that it must be done before the SEP rating expires.
No, Mach Jump was spot on.
An SEP is valid for two years but to revalidate it 'by Experience' the experience must all have been gained during the second year of the two year SEP validity period.
From what he has posted, Andrew2487 did not allow his "Bi-annual revalidation flight to expire" as it was never 'valid' for Revalidation purposes as it took place the 'wrong side of a deadline'.
NB: Not sure what he meant by a "2 yearly deadline".
Andrew,
Unsure what other qualifications you hold but note that a successful Flight Test (of any length, for any Rating) can replace the one hour Dual requirement for SEP revalidation by experience. Have you passed any Flight Tests within the second year of validity of your SEP?