How closely to the deadline should I expect professor to submit reference letter on my behalf? I asked a professor to write a reference letter for me and he agreed to it; however, the deadline is coming up and he has yet to submit the letter.

As I am not experienced with the process, I wanted to ask if, based on your experience, it is typical for professors to delay submitting references to the last minute.
I find that the approach of most people I know people to letters of recommendation falls into two general categories:


Do them very quickly, so that you don't have to think about them any more.
Forget about them until nearly the deadline, and then submit them at the last moment or slightly after (once reminded).


Lots of people, including lots of professors, fall into category #2.  The question is, how do you make sure the letter is on time without being a pest?  To this end, I recommend giving three reminders:


A week before the deadline
1-2 work days before the deadline
On the day of the deadline


This balances respect of the person's responsibility (not too many) with minimizing the chance that a last-minute reminder will be too late.  It's the same sort of frequency that I use for reminding people about seminars and other things where you want to balance between awareness and annoyance.  One might tweak the formula a little, but the general principle of increasing frequency near a deadline is the key.