If you stay past 38 now there is an increased chance of you filling a non-flying related job (what are we at 40 FE@R or so across the FW board) and therefore risking/ losing your flying pay.
Orca,
I'm probably just being thick (it's just the festive wine, honest!), but surely most people who stay past 38 will be PA and therefore won't be getting flying pay anyway?