Scheduling depends on what kind of service you work for. In my area 911 providers work a 24 on/48 off shift or 48/96. Private services around me usually staff a couple 12 hour trucks, a 16 hour truck, and a couple 24 hour trucks. Again, it all depends on where you are and what you want.
International work...I don't know anything about nature trips, but most oils field and contract military stuff is for seasoned paramedics.
Whatever you decide to do good luck to you! And, from an old seasoned medic, make sure you find healthy ways to destress before you are too far in. This is a hard job and it takes a toll over the years.