After reading all the posts for/against long/short time requirements...
...I've come to conclusion that the long timer I am wanting is the way to go. There are no good arguments for having it 100 days, and many good arguments for having it 200-365 days. I'm also leaning towards accepting the idea of in-game timer as well as 100+ days after adult RoP timer; the latter being essential IMHO.
Some say it'll take a long time for a casual gamer to build a dragon up to these reqs. However, for these same casual players it will take a long time to build up a 100/100/100/100 biped adventurer. Ancient status is dragon endgame in similar manner to 3+ capped classes are for bipeds. Neither should be achieved easily.
Others say it is too long, they'll be left with nothing to do while waiting to fulfill ARoP reqs. This is a separate problem, lack of game content and entirely AE's headache not ours, and as such should not impact discussion ARoP requirements (not relevant). Even after completing the Rite, you are stuck with the same perceived problem of 'nothing to do'.
Incidentally, this suggests 365 days is a suitable number as it divides opinions between casuals and hardcore. Add the other two timers and we should be set.