Hmm. Semantically speaking when one says that they are a 'Professional Programmer' all that says to me is that they are in the programming profession (e.g. they recieve a salary from a company for preforming programming related duities). So, to this end, anyone that is currently working as a programmer would be labeled as 'Professional' and, therefore, experience has nothing to do with it (outside of having secured the position in the first place).
The way that you posed your question, it seems, is that you are asking how long does it take until one can consider themselves a Mid level to Senior Programmer and, as you said in your post, it varies from developer to developer. Typically, in the US, companies are looking for a minimum of 5 years experience when they are looking for Senior level developers.
Does this answer your question a little bit?
-Doug
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Doug Parsons
Wrox online library: Wrox Books 24 x 7
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