Have been dreaming of it since I was at least 15. Hell, there was even a time during my period of trans denial where I refused to admit to myself that I was trans where I still thought of possibly getting it done, because my bodily dysphoria down there was pretty bad pre-hormones.
Realistically, right now I'm completely broke and jobless, plus my mom and dad probably aren't going to help, since Mom has no money and Dad isn't very supportive. So although I'd love to have it done as soon as my one-year RLE mark passes next April, it's probably going to be YEARS before I can afford it, unless something huge changes.
So yeah... 13 years of wanting it as of now, and by the time I can actually get it done, it will have been about 4-5 years of actively trying, possibly longer depending on how my financial situation ends up.