Hi Prasad
"check whether the job is scheduled since long or lately". - means that for how long this job has been running, that is, before this instance or someone recently realized that this job is not executing and started it....and it picked up all the deadlines?
Was there a recent change in the workflow definition? check SWDD and last changed by in the header of the workflow...... but that should not be the cause as old workflows continue to run with older versions.
Can you give a screen shot of the technical WF log, select that decision step and select the tab "Step History"....expand all cols and all rows in the screen shot.
Regards,
Modak