As mentioned, JSS is a big surprise that no one knows what it will bring.
However even when I was at the bottom of the pile I still regularly got destinations that I wanted. You can further massage your roster by swapping trips. You can also shorten or extend your trips by sector swapping.
The aircraft is a dream to fly and 99% of the pilots on the fleet are quite frankly brilliant to fly with.
You will be working very hard. Your days off are often spent recovering. Actually when I did my sim assessment the trainer said to me "you will learn what it's like to be tired all the time" but you adapt. Well most people do.
A "standard" roster is very difficult to produce as everyone wants something different.
Just make sure you make the most of it when you're down route. You're a long haul pilot. Explore the world