I have 2 - 1 between my shoulder blades of the symbol of the Cherokee nation (I am only 1/4 Cherokee, but the more I learn about this part of my cultural background, the more I find I identify with Cherokee values. Maybe I should also note that as a mutt, I'm not more than a 1/4 of anything) and a large one on my lower back (yes, tramp stamp) of 2 horse heads facing one another and forming a heart.
I spent years looking for the design for my first (and smaller) tattoo. I chose my second, large tattoo fairly quickly, but the concept of the image was one I had seen and had in mind for quite a few years (not as a tattoo, just as an image).
For anyone considering a tattoo but concerned about what it will look like as you get older, it is possible (and often recommended) that you get them touched up as you age (think 10+ years down the road, depending on how old you are when you first get it, the amount of sun exposure it gets, etc.). Plus different colors fade/bleed at different rates. Both of mine are done in black, which is the most stable. Red fades the fastest. For other colors, ask a reputable tattoo artist. If they aren't willing to talk to you and answer your questions, you don't want them putting a needle in your skin anyway.
Ultimately, when people thinking about tattoos asks me if they should get one, I tell them find what they want done first. The image should mean something to the individual, and remember that the person you are today isn't the person you'll be in 10 years (not just physically). Consider where you want it. How much will it hurt there? What will happen to it in that location as you age? For example, a tattoo on your belly will stretch/shrink as you gain/lose weight, and it will hurt. For women, if you get pregnant after getting a tattoo on your belly, will you still like it with stretch marks through it? If you find or draw up a tattoo that you like but still aren't sure, set it aside and wait a year. Ask yourself again if you want. Still not sure? Wait another year. If at this point you are certain you want it, go for it! If you're still not sure, chances are that either this isn't the image for you, or maybe tattoos aren't for you.
Tats aren't for everyone, but I got mine for me. I already have my next one planned, and that one has special meaning for me too. I don't see myself ever regretting them, and anyone thinking about it, you don't want to regret it either.