How long should you wait for an elevator?

Jason, a loyal MR reader, asks:

Google wasn’t able to help me here.

I figure that the longer you wait, the shorter the expected remaining waiting time.

However, in the worse case, if the lift has broken down, the waiting time could be infinite.

For an individual lift, one could, I suppose, collect some stats on average wait times, but I’m interested in the best strategy for an arbitrary lift.

The technical approach is to model the arrival of the elevator as a mathematical process, set up the problem, and solve it.  The seat of the pants approach is to ask about your psychological biases.  Are you, in the first place, more likely to spend too much or too little time waiting for elevators?  In my view standing and waiting isn’t so bad, provided you have something to do or think about.  So my advice is this: once you start waiting for an elevator, begin to think through some interesting problem you face.  The ideal is that when the elevator arrives, you will be disappointed and of course that means you have hedged your risk in the first place.  The question that people screw up is not how long they should wait but what they should do in the meantime.

If you’ve finished thinking about your problem and the elevator still isn’t there, take the stairs.

Readers, what do you advise?  Is there a second best case to be made for "elevator waiting indecisiveness," or should you just have a simple time rule and stick with it?  Is there a formula based upon the number of shafts and number of floors in the building?  The frustrated look of the person standing next to you?