Whether or not the STN boom is shortlived or not, that airport will still have had the benefit of having them along with the jobs they have brought. Hopefully it will continue thus. Although MAN isn't exactly quiet, growth seems a bit stagnant, particularly longhaul. MAN really needed a big LOCO, by which I mean Easyjet.
Also STN must be looking very profitable for BAA, 23,000,000 plus through 1 terminal smaller than MAN T2.