Outlining tattoos

Is outlining a tattoo a must? When I was younger and contemplating getting tattoos, I always thought up fanciful designs, but then got discouraged when the idea that a black line needed to be wrapped around the entire thing. I've gotten over that since, but I was wondering, do tattoos -really- have to be outlined, if so, do they have to be outlined in some shade of black? I know of a great deal of tattoos that don't have any outlines, but my main concern is if they bleed more or less over time. I'll add a caveat, that I'd prefer actual photos or reliable sources in this, rather than opinions or rants for one side or the other. If you've tattooed for a long time, then I really value your first hand experience. Cheers, Ahlyn

Oh, I'll add that by bleeding I mean color, as in the fuzzying of lines over the lifespan of the tattoo, or any other related problems

There is a huge, ongoing debate over this topic in tattoo circles. My opinion, is that it's not like drawing a line around somethings suddenly creates a majic border that makes the tattoo hold up. If everything but the black line fades out into nothing, then the tattoo with the line will look even worse than one without one. What seems to hold up over time is size and contrast. Too small, and the details bleed out; sharp contrast helps even time faded images to stand out. Staying out of direct sunlight, or wearing sunscreen helps as well. I'm sure you've seen posters in deli windows that have bleached out with exposure to sunlight, tattoos do the same thing if you don't use sunscreen.