From a Southern Air guy:

We work 20 days a month. We normally fly 2 laps around the planet, that comes up to 70+ hours and takes 14 to 17 days and then we sit reserve until we reach 20 days at no extra pay since we already broke the 70 hour mark.
When you are junior the odds of getting a back to back (40 days out) are pretty good.
Upgrade right now is 10 years on the 777 So if you are planning to build PIC time. That is not going to happen.
Junior assignment happens a lot and cannot be refused. If crew scheduling talks to you, you cannot say no.
Our medical is poor at best but is pricey.
If you do commercial you will get coach and the odds are good you will get to enjoy a center seat. They always buy the cheapest seat available.
Just say no