On a tangent, does it really take 15 years before you can start tossing about the phrase "senior"? The only job ads I see asking for that kind of time appear to be aerospace/government, so I'm curious if it's just the startup bubble making me think 7 years is fine?
To have "senior" appended to your title, no -- that is basically nothing, and means as much.
To be a genuinely "senior developer | engineer | programmer" in the eyes of others it probably takes at least 15 to 20 years of experience building and running things. Not all of that needs to be professional - writing door games in high school counts.
