It was many years ago now but I accepted promotion at 38 and then got stuffed with a posting to MOD! In those days one had to do 3 years to amortise the promotion but after a few months they changed the rules to 2 years! Tongue in cheek I told them I was leaving after the 2 years was up and expected a full pension! They told me I was signed up for 3 years so had to complete my tour in MOD before retirement!
A lot depends on your age and what you plan to do next. If its an airline job then every day lost is at least one place on the seniority list so it may be best to go as early as you can!
Whatever you decide be prepared for some 'blunty' to mess it all up!!