How long did it take until you upgraded from your beginner DSLR to a professional one?

I got a nikon d3100

Why would I bother?
Huge expense for features I don't need!
The pro cameras are built to be extremely rugged so they can stand up to the rigours of professional use. A professional probably gives his camera more hammer in a day than I give mine in a year!

Quite happy with my entry level EOS450D and when it dies I will replace it with an equivalent model.

How long will it take you to be able to use your camera intuitively?

In other words, when your camera becomes an extension of your eye and you no longer have to think about how to get perfect exposures in the manual mode and you have lenses from super wide angle to extreme telephoto that you are using on a weekly or even daily basis, you will have a strong urge to buy a Nikon D4.

Between the D3100 and D4, I'm sure you will have purchased other camera bodies like the D7000.

It took me just about five years to gather enough skills to become a professional photographer. Three years of intense education and another two years working as an assistant staff photographer for a large corporation.

Form that point on, the learning has continued and the tools I require to complete assignments from shooting professional sports, editorial and industrial/scientific.

Since I consider all dSLR's to be basically the same at the same time that my preferred brand doesn't really make entry-level models (because they just make two each time, one expensive and one not so expensive) and since I can't afford the expensive models, it took me just one year after I bought my Pentax K200d to buy a Pentax K-x for the simple reason that I realized that my K200d was too good to be true and that to prolong its life for my serious (paid) shooting assignments, I had to get the K-x for my less serious (charity) shooting needs meaning I didn't do an upgrade (how does one upgrade a dSLR anyway when in reality it's called replacing) and just went for a backup but if the K200d was still available at the time I bought the K-x and if they weren't priced very far apart, I would have gladly bought a second K200d for horsing around.

My beginner DSLR is a Nikon D90. I don't anticipate outgrowing it in this lifetime.

I spent two years with a Praktica before upgrading to the Pentax I really wanted (viewfinder information, better meter, faster lens changing) back in the days of real cameras.

My current EOS 350D does everything I want it to and will be replaced at the end of its natural life by something similar, probably another Canon that will use my existing lenses.

Your D3100 will do anything you need, if you learn to use it properly. Take it from someone who's used all manual cameras from the beginning