High anxiety is spreading among developers and lobbyists desperate to get their projects approved by City Hall before Mayor Bloomberg leaves office.

The Bloomberg administration has more than a year to go before the packing crates come out.

But insiders said that might not be enough time for land-use and other applications to wind their way through the bureaucracy.

“You have until December,” said one lobbyist. “After that, the door starts closing. People are very focused on pushing their stuff through the pipeline.”

“There are projects lined up,” agreed another longtime lobbyist. “People are trying to speed everything up. Who knows what happens with the next mayor?”

Case in point: As his final term was coming to a close in 2001, Mayor Rudy Giuliani announced a deal to construct new baseball stadiums for the Yankees and the Mets, with the city and the teams splitting the $800 million cost.

Giuliani didn’t make the agreements binding on Bloomberg, who ultimately decided the city couldn’t afford to proceed during the fiscal realities right after 9/11.

Both ballparks eventually got built under completely revised terms years later.

On the flip side, once a deal is signed and sealed, it’s difficult — if not impossible — for the next administration to undo it.

As his term was ticking down in 1993, Mayor David Dinkins cut a contract with the US Open to construct a new tennis stadium in Flushing, Queens.

The incoming mayor, Giuliani, wasn’t happy about some of its terms. But, in the end, he decided there wasn’t much he could do about it. The contract stood.

Another concern for those doing business with the city is the brain drain that comes with the wind-up of every administration. The biggest question of all, of course, is who’ll take over when Bloomberg departs at the end of 2013.

One source said a half dozen senior city officials are already circulating resumes.

“You don’t want to be the last one out,” explained the source.

Those who have worked with the top officials for years are understandably jittery about developing new relationships with their replacements.

With five solid Democratic contenders in the mix, those trying to plan ahead are in a bind. A government headed by, say, City Council Speaker Christine Quinn is likely to have significantly different views on many issues than, say, a government run by Comptroller John Liu.

“People want certainty,” explained one lobbyist. “Right now, there’s a lot of uncertainty.”