How often to Audiophiles upgrade their equipment?

A serious reply.
I have had systems since 1965.That first one lasted 15 years when I sold everything and moved across the country.
Another pickup system lasted about three years, it was all junk but provided music.
I started my current system in 1984.
I totally got the bug and sold all the starter stuff and moved up, I bought some Infinity RSIIa for $2,200 on sale. they lasted 20 years. I just 4 months ago tore them apart to sell the bits and pieces as I got WAY more money for those than I would have for the whole speaker system.
I am using some Maggie MGIIb I got at a steal price of $200. from a LOCAL dealer, clean and new covers!!
My amp bought new when it was raved about ?? 10 years ago?? it is a Forte 4a amp that is all I will ever need, for ever unless it breaks. same with cables. I do not play cable flavor of the day.
I dumped my Counterpoint pre because it broke twice, and got a SS Adcom. That was a few years ago, and again it will be it until it goes to stereo heaven.
I added last year a Sony SCD777ES player and sold my Rotel transport that was 4 years old.
I wore out a Sony 87Es 5 disc (played everyday all day while I was gone for my pets, for 10 years) and bought a replacement in a Sony 7Es, added a Sony 9ES that was a sudden opportunity/steal at $110. (again for my pets)
The last six months just got into vinyl and a used AR pre pre , Denon 59L and Dual golden one plus an Ortofon OM20. and LPs lots of used LPs.
The Maggies are currently using automotive wire for cables because the AQ midnite cables I have need retermination.
So the NEED vs the DESIRE can be difficult to determine.
I say if you HAVE to spend something, buy ONE really GOOD thing at a time. Instead of a bunch of slightly better stuff together.
Say a dynamite pre that you can say will last you at LEAST 10 years.
You do not have to plan to have a system that the cost is more than a new Mercedes!!
Think about what level of stuff YOU want, and stick to your plan. I do not NEED better stuff at all.
I probably will replace the Maggies with something in the $3,000 area in a year or so. Right now I am grooving on the LPs I am totally into that.

I guess I fall into the camp of making fewer changes, but more material changes when I do make one. Like Rcprince, my equipment usually stays in my system about 10 years on average. (I lived with a beautiful pair of updated Marantz 9 amplifiers for 25 years. Speakers on the other hand seemed to have lasted about 8 years on average.) I have avoided making minor incremental changes in favor of fewer more significant upgrades. I've also consciously limited myself to a single system so any of the limited financial resources available could be maximized in that one system.

On a more serious note, the idea of making fewer significant changes is one that probably will minimize your $ outlay and maximize your enjoyment, unless you have $ to burn. Someone much wiser than me noted on this forum that you should plan on doubling the cost of the component you replace (on a new vs. new or used vs. used) basis to make a significant upgrade and my experience shows that that is pretty close to being correct, at least in the middle of the high-end market (wherever that is).

Ever since i had gotten out of the military, i would upgrade whenever it made sence economically.
Several times i had a chance to upgrade in the past 2 years and i diddnt because i had other priorities, Before that i would Make 1-2 major purchases in my stereo over the course of the year.

No all i have is radioshack speakers, a decent preamp, and a denon amplifier that keeps producing occasional static when everything else is off, i keep expecting it to explode, so right now i really really have an upgrade bug.

Once i get myself a decent rig i will probably go another year before any new purchases.

First i need new speakers, amp, pre, etc. probably gonna build it myself. Tube stuff most likely.

Maybe a year after that i will look into getting a turntable some some blues on vinyl.

One more thing.
Really be happy with what you have now. enjoy it, even if it has some shortcoming, who cares!!! just listen to the MUSIC, not your system!!!
Some folks get so into the electronics they can't enjoy anything anymore... all they think about is how to make it sound better. They never get around to just having fun enjoying some music.
(Though once I made a bad purchase choice, and after the fun of a new toy wore off I realized I had almost totally stopped listening to music. I had to think out what happened and realized that the pre I bought was crap, (A Sony ??1000 thier first digital processing pre)
The Hafler DH110 before that was a really pleasant pre. the Sony, after the fun of the bells and whistles wore off, sucked.)