First milestones
Funny, as you are learning the "first solo" is all you can think about but as I look back now with my 90 hours (yeah, still very inexperienced tyro) the first solo is not the begin all and end all. What about:
Hours to:
1. First Solo
2. First Solo Nav
3. QXC
4. GST
5. First international flight
6. First flight in another country (i.e. not flying from home base to abroad)
7. Managing to scare yourself !!!!!less
8. Finding something in the nick of time that was VERY dangerous (fuel in water, wrong pressure setting on altimeter, realising you've got the wrong airfield etc)
9. becoming lost for the first time (luckily still not had that yet although I've been sure of position to varying degrees over the hours)
10. Flying with somebody else and being less than sure of their flying ability.
11. Posting something on pprune that generally receives a positive response
12. Allowing somebody else control for a few minutes (still not done that one, nobody I fly with wants to touch the controls even if I were willing).
Whilst I can remember every second of my first solo like it happened 5 mins ago, there are so many milestones in aviation. Some much more interesting, some down right more terrifying.