It makes the Spanish system seem very sensible.
I think, with respect flowman, that you're letting your hypothesis get a little ahead of you. In the unlikely event that Spanish ATS does do some sort of check on FPL, wouldn't it be just as easy to perform the validity checking from EOBT-30 to EOBT+30 (which is the conventional ICAO validity period) or EOBT-15 to EOBT+15 (as required by CFMU) rather than EOBT to EOBT+30?