A quick reply to a couple of earlier questions/comments:
S/O's are not required on flights over 8hrs. Any crew complement that meets the legal requirements will suffice. Many long-haul flights are, for example, crewed with 2 F/O's and 2 Cpt's, or 3 F/O's (one of whom must be 'RQ' relief qualified) and 1 Cpt.
S/O's are (not meaning this in any negative way!):
- a way for the company to hire crew for less money (initially, at least)
- a way for the company to hire crew with less experience (ie cadet program, where they don't meet the regulatory requirements for F/O licensing)
The two are intertwined of course, as less experience = less money
There is a training bond of 7yrs applied to the Cadet Pilots. The company expects a minimum of 7yrs productive work from you in exchange for their substantial investment in your training. Of course they gain from this arrangement also - see above comment on less money.