Consider a simple queue model like the one described in <http://en.wikipedia.org/wiki/M/M/1_model>. The article states what the expected waiting time is before a request enters the queue.


Assuming that the actual queue length is unknown, does the expected value of "time left to wait" for a given request change over time while the request is in the queue?


**Clarification**: is it true that the expected time until a request is served stays constant, regardless of how long it has already spent in the queue?



Does waiting in a queue change the expected time left to wait?
I am not entirely sure what you are asking but ...


The model you reference in the wiki article has a memory-less distribution for waiting time and inter-arrival time. Thus, the total time for a request to get processed is not dependent on time. 


