It's the time of year when otherwise sane people need to be reminded that April 15 is just another fine spring day. There is absolutely no urgency to filing your return last week, or this week, or next week.  If you expect to owe money, you can pay a small amount of interest for the privilege of leaving your cash in the money market at 5% for a while, or you could have sent it with an extension at some time in the last three months.  

So many tax practitioners encourage this kind of irrational behavior.  Traditions die hard.