Tattoo touch ups are not as common as you think. As a matter of fact a good tattoo hardly ever needs a touch up.
With that being said. When we do a tattoo we ask the client to come back within three weeks to check for any touch ups that may be required. Some folks come back after a month and we still validate them. 

Some folks try to come back after three years with visible sun damage + farmer tans and expect us to repair the damage they've done. This does not sit well with us after we explain to clients that once you get tattooed the sun is your enemy for life. Here are the common questions they ask...

"what about sunblock?"
Our answer is always the same, the sun will burn your ink. It doesn't matter if you getable the sunblock lotion in the world, Your tattoo will fade, look at a cars paint job, a ton of cars have sun damage to their paint, and cars have clear to protect it. Sunblock is not going to save your tattoo. Sure sunblock is meant to protect your skin from uv rays, we are not denying that, but its not going to save your tattoo. 
 
Should I keep it out of the sun till my tattoo heals?
No you should keep it out of the sun for life!

What fades faster a color tattoo or one in black and grey?
A well done tattoo should hold up in either style, keeping it protected from direct sunlight will preserve your ink, the sun will make it fade.

What about traditional tattoos v.s realistic, which ones fade faster?
We tattoo in every style its also the clients responsibility to properly take care of their fresh and healed  tattoo.  When clients follow instructions we never have  issues. When not properly taking care of them even traditional tattoos fade or look blurry.