I'm no expert on this but I wouldn't recommend it. For a number of reasons (which are stated in the attached links), you have to wonder why a, basically, maintenance-free material like ceramic tile should be 'turned into' one that now requires maintenance. To me, and to me personally, doing this to tile defies the point of having ceramic tile.
I understand that you don't like the look of the tile. The key to your question is what you already asked - How long will it last??! Remember, you will be walking on your 'newly-painted ceramic tile floor', and you have to realize that it will wear a lot more than a regular, ceramic tile floor. YOu could be at this painting every hear depending on how you 'use' your kitchen. (Dogs, kids, dragging, dirt & grease, etc., etc..) Apparently, as stated in one of the links, it's possible (but I have never checked into this particular type of job.) At the same time, you'll probably find as many people that don't recommend this type of job. I guess if you ask any painter, he'll say do it. (Well, with all due respect to the Painting Pros out there, the answer may seem self-serving when they say it can be done.)