If the past is prologue then President Carter's semifreeze on government hiring has a maximum effective life expectancy of about 30 days.

After that, the forces of natures in Washington - Congress, the bureaucracy and special interest groups - will have had enough of economy and demand a rapid thaw.

On Wednesday, the President told all federal agencies that they could fill only three jobs for every four vacancies that occur. The order is back-dated to positions vacant from Feb. 28 on, and is expected to run until April. Idea is to trim some federal job fat until new personnel ceilings are announced for individual agencies.

What the Carter people need to know, if they don't already, is that this sort of thing has been tried before and always fizzles - often killed by the people who started it - if it runs too long.

Back in the early 1960s, the Senate said it wanted to trim federal fat. LBJ said fine. It voted a similar 3-for-4 hiring freeze. It worked for about two weeks, then quickly fell apart.

The first crack in the freeze came when Congress with White House blessings exempted the Defense Department from the hiring freeze. Defense was 50 per cent of the government.Next came exemptions for the U.S. Postal Service and the Veterans Administration. That was 75 per cent of the government.

Finally congressional, bureaucratic and lobbying pressure brought exemptions for the Federal Aviation Administration (nobody likes plane crashes), and the FBI (nobody like crime), and the Internal Revenue Service (the government needed the money).

By the time all the exemptions were in, the only agencies that still were bound by the freeze were places like the Bureau of Public Debt and the Marine Mammal Commission. The rest of the government had been thawed, into a new life of hiring.

Years later, the wheel was rediscovered. This time President Nixon ordered a 90-day freeze. Guess who broke it? The White House quietly asked - and got - an exemption from the White House-ordered freeze so that people near and dear to the White House could be hired by "frozen" agencies.

The lesson is that all of us are for government economy, even hiring freezes, so long as it doesn't affect us, or our business, in any way. When it does, and it usually does, the ice breaks up quickly.

Federal officials note that another interesting thing happens everytime the government freezes hiring to get some breathing space via attrition. Attrition almost stops. People who would have quit or retired tend to hang onto their jobs until the freeze is over. That's a statistical fact.

In "normal" times, anywhere from 12,000 to 15,000 federal jobs become vacant each month, but the normal quit rate goes out the window whenever there is a federal job freeze. This is because would-be retirees become nervous and individuals who are seeking other jobs tend to stay put until the outside market - which is affected by the government job market - stabilizes.

So government-watchers give this semifreeze about 30 days of effective life before Congress, or the bureaucracy, or ordinary taxpayers demand a thaw.