if nothing goes wrong...Trader comes early so you must ensure the system could function early!!So if there is a problem, you must solve it either by the end of the trading day or before the start of next trading day...
if the system cannot function...10 million dollar may loss...if you cannot solve it, you are fired...
And you will have to deal with a lot of ridiculous questions. And if you support a very lousy application...god bless you
For developement team, at least you still have the support team to act as a buffer :) and there is not always a project, so usually you will get serveral week break before next project release