Some years ago the company I was working for then brought in a new support manager whose experience was in engineering manufacture but not IT. He devised a new system for categorising faults based on their priority from Critical down to Trivial. These were reviewed every week in a Monday morning meeting where he defined the order faults/bugs were to be tackled. After some months some of us (bug fixing taking around 20% of my time) asked how much time needed to pass before a trivial bug was upgraded. His view was never. After he had been there some more months major clients (major financial institutions and others) started shouting loudly about the trivial bugs and work arounds. It was not long before he joined the job market!

Many factors come into deciding timescales!