I have long hair, I will continue to have long hair. I like it. That's all that matters.
I would say if you want to let your hair grow out and it is a different color, drastically different, then perhaps a good way to do that would be to do a frost on it. The frost would disguise the roots growing out, it would make the line between dark and light less noticeable, more blended in, etc...I have done that before and liked the way it transitioned.
BTW, everyone in my mom's family was totally white by 30. I however took after my dad's side of the family. I looked forward to the day I started turning grey. I'm 53 and now have a few. YEAH!!! I did always wear my hair frosted a lot. I liked the blonder look but only did a pure white frost, I hate yellow blonde. It looks cheap to me.
So I say go to Walmart and get a frosting kit. Have a friend who's not afraid of pulling some hair through a cap, have some fun. It can always be died dark again if it gets messed up. I think a light frost at first then going towards a heavier frost as it gets lighter and lighter.