I'm in the top 10% after 16 years (first few years were part time). I should break up to top 1.6% next year or two if things go well. Not too bad for a single mom! In my last position, I was so desperate trying to get out of there and hoping I could at least make it to 25 years and hope even more for an early out, that I was putting everything I possibly could into the traditional. Now that I've moved on to a new position, no commute, love my job and schedule, I'm much more relaxed about staying until my MRA (57).
I ran so many calculators, etc, that I decided recently to lower my contribution to 6% and focus on finally building my house instead. For now, anyway. Maxing out in the beginning (when max was 12%, not a dollar amount), and increasing every year, means that I can lower my contribution at this point and see very little change in the difference of the contribution. If I add the very low end of my pension + tsp + other factors (no mortgage if I sell current house after building new house, etc), I end up with monthly income so high I'm not sure how I could spend it all. And that's even with my now-reduced contribution. It's a very good problem to have.