What I've heard...
13 rosters, everyone 28 days. In this roster you have 3 and 6 days off in two blocks, both blocks have 24hrs rest in front so effectively you have one block of 4 days and one of 6 days. 42 days vac a year gives 3,23 days/roster (min 12 hrs rest before) (although you have to take min of 5 days).
This gives in average 14,5 days REST/OFF/VAC per 28 days roster. If you're lucky you have one or two blank days per roster. The rest of the time you can consider being on the road.
With low seniority you very seldom get to south America and USA, Australia and New Zeeland, but end up in Africa some, but mainly Asia.
Is this what you expected?