http://www.dbstalk.com/topic/171096-mitsu-dlp-lamp-warm-up-time/

It's a shame more isn't known about the history on your set but I am encountering folk that had some LED HDTV and when they get a model with a bulb they think something is wrong with the start up time.

In short, I see nothing wrong here except the support that didn't care to explain it.
Bob