What government agencies are out there mass-building wind? In terms of America at least, that's not how our generation system is set up.

Also, the recently-published Wind Vision[1] runs with an expected 20-year lifetime, and starts digging into system reliability specifics on page 70. Wind Vision was a lengthy collaborative process with industry, the labs, and DOE HQ. Good news is that there have been significant reliability gains in the gearboxes, generators, and electrical systems.

[1] http://www.energy.gov/windvision .pdfs are on the right.