Updating skeletons at every start? (slow)

I'm using PyCharm 4.0.6 with a Python interpreter from a virtualenv (which sees both system-site-packages and some that are installed inside the env).

Each time I start PyCharm and load up my project, it goes through a lengthy (~few minutes) "Updating skeletons..." process.

Does this really have to be done each time I start PyCharm? Is there a way to disable it, and if so, what functionality will I lose?

Cheers,
Elvis