Six months can be a lifetime, or at least actually 18 months

Any programs started under the FISA expansion bill last for one full year after the bill itself ends

Wired magazine weighs in on why Congress’ “temporary” six-month expansion of Foreign Intelligence Surveillance Act powers was so dangerous:

A new law expanding the government's spying powers gives the Bush Administration a six-month window to install possibly permanent back doors in the nation's communication networks. …

Prior to the law's passage, the nation's spy agencies, such as the National Security Agency and the Defense Intelligence Agency, didn't need any court approval to spy on foreigners so long as the wiretaps were outside the United States.

Now, those agencies are free to order services like Skype, cell phone companies and arguably even search engines to comply with secret spy orders to create back doors in domestic communication networks for the nation's spooks. While it’s unclear whether the wiretapping can be used for domestic purposes, the law only requires that the programs that give rise to such orders have a “significant purpose” of foreign intelligence gathering.

Plus, Wired notes this is actually an 18-month bill:

The law … makes any program or orders launched in the next six months perpetually renewable after the six month "sunset" of the new powers last for a year after being authorized.