Current s/o's doing between 24 to 32 days per 56 day roster depending on seniority and their preferences ie. longer trips with more time in ports, or shorter trips with quick turn around times. F/O's and Captains are similar. Shortest trips are about 4 days, longest are 14 days for S/O's, average trips are between 6 and 8 days long.
767 F/O's are doing anything from day trips to 6 day trips, while I think the longest trip for a 737 F/O is 4 or 5 days.
You can get good coin if you work 900 hours per year, but as to how much it varies greatly between individuals and aircraft type.