Be extremely careful when getting Kanji characters as tatuagens if you've found the design on the internet or tattoo parlour wall. You may think it means "Peace, love, harmony" but for all you know the characters could be straight off a soy sauce packet, or worse.
Most tatuagens will need touch-ups through your life. Using sunscreen and moisturizing daily will help your tattoo look new for years. After 10-30 years, expect to need touch-ups to combat blurring. If the thought of doing this over wrinkles when you're 75 grosses you out, this could be enough of a reason to not have one.
Think about it....