As a new joiner form the last recruitment drive on the 747 a few years ago I can confrim most of what's been said before.
BKK-SYD is about as senior as it gets. I've not done one at all. I don't like being away for 9 days, so don't want to do them.
SIN, CPT, JNB occasionally drop all the way to the bottom, but probably about once a year each in my case.
Tandemrotor gives a bit off a reality check with what you can expect. The 744 is the most senior fleet in the company, so if you join that fleet at year1, like I did, it'll be a fair while until you get some control. Not unfair I would say, considering most people in the company had to wait years to be able to move.
Having said all that, there are so many possibilities to tweak your roster by using the system. Trade with other people, trade with available trips in the computer, use the week off reserve gives you etc.
The 744 has got such a big network that it feels like I never go to places "often".
To give you some perspective, Mex is considered one of the least popular places, but it's horses for courses. With my lack of bidding power, to work the same hours as the MEX, I'll have to do two 3day trips like JFK, BOS, LOS. So two 2man night flights versus sitting by the pool in MEX for a few days or even taking a fligt to cancun and chill out there...