SL,
Just about all the larger companies do exactly as you suggest (albeit for differing timescales), as do most twin operators. The problem is that many FI's looking to get the turbine opportunities are self employed and have no contract let along one that bonds them (FI working conditions have been discussed lots on this site before
)
The knack to getting that all important break is having the required qualifications, AND most importantly knowing the right person at the right time.
FW