An east coast USA trip will leave UK pm day 1, nightstop USA that night, return the following evening US time, arriving home roughly 48 hours after departure. West coast trips add a day to that. Far East flights vary, depending on the schedule. The longest trips (Shanghai, Delhi, some Caribbeans) currently have you away from home for about 5 days total. Australia (if and when it turns up) will be around 9/10 days. Time off depends on the length of the trip, but is a minimum of two days post-flight (not including the day of arrival).
Hours are contracted at 750/year. To achieve that with leave, sim, courses etc, requires rostering at about 80 credit hours/month, or around about 70 flying hours in a month with no leave scheduled. A JFK represents about 15 flying hours, Hong Kong is 25 or so.