Well I currently have two 70's Holly Pally & PoM Pyro Mage. Mage took me about 10 hours a day for like 7 days. The pally took about 3 month but I scrued around most of the time.
Pally 15 Day play time... 70 at 11 days
Mage 7 Days play time... 70 at 5.5 days
I used Joana's guide on the mage...
1-20 is like 8 hours. (Semi-Fun)
20-30 is like 10 hours. (Meh)
30-40 is like 10-12 hours (FUN)
40-55 is like 30-40 hours (BORRING)
55-60 is like 3-5 hours (FAST & FUN)
60-70 is like 50 hours minimum (Fun but looong)
It's worth it if you have free time, and it does get addicting. Not to me but still lots are addicted.
BTW the record is like 4 days 20 hours. 1-70 and 18 hours and 24 mins from 60-70.
Play wildhammer on horde.