How often to Audiophiles upgrade their equipment?

I am eternally confused as to how and when I should spend my money. I started into this hobby a little more seriously about 3 years ago and have the bug in full now. I do very much enjoy listening to music. However, there is always confustion on how to spend my money. I am not being very clear. Let me start again.

Currently I have a home theater setup in the family room with a Rotel RSX-972 reciever, B&W 603S3 mains, LCR600 CC, ASW1000 SW, 602S2 surrounds, Sony 999ES DVD/SACD and Sony KP51WS500 TV. I have started a second budget system in the main living room for music only and it has Monitor Audio Bronze B2 speakers, Rotel 1060 Amp, and Rotel 961 CD player.

I am generally quite happy with this setup and enjoy them very much. But off course I am always thinking what can I do better and if I should at all. Having a young family, I doubt I will ever buy some of the very high end euipment or if I would want to. But I have an opportunity to uprgade my speakers now with a very small loss. I was thinking of the 604S3, but having looked at them, they are just too big and frightened me off. The next step up to the B&W CDM series is quite a bit more. But to go to that line, I should probably also upgrade my amplification first.

I guess what I am getting at is, how long do "real" audiophiles stay happy with their equipment and when do they decide it is time to upgrade. For example, I was thinking of always sticking with a budget, and stick with my equipment for say 5 years (unless their is something terribly wrong) and then get new equipment/newer models different brands but using the same amount of money as in the original budget five years earlier.

If this question makes any sense, please relate your thoughts and experiences.