(Dow Jones) New tax rules in 2011 will make it very worthwhile for some people to give big gifts to friends or family. Tax advisors are helping them decide how soon to act because, as advertisers like to say, the opportunity may be limited.

When Congress extended the Bush tax cuts late last year, it also included big increases in how much a person can give away tax-free over his or her lifetime. Since 2001, total gifts over $1 million resulted in a tax. The new ceiling is $5 million, at least for this year and next.

The new rules last only through 2012. What happens then is anybody's guess, so many wealthy taxpayers want to make sure they give away $5 million--plus all growth and appreciation on that gift--while the giving is good. For married couples, there is $10 million at stake.

The issue is "the hottest one out there, by far" for tax advisors, according to Robert Keebler, a certified public accountant in Green Bay, Wis.

The very wealthy who can afford to part with $5 million, or $10 million for couples, without strain should certainly give away that amount in the next two years, according to several advisors. Gifts also make sense for some who are affluent but not extremely rich. Where a person resides makes a difference, of course, because cost of living varies.

Who shouldn't give? Single or married people who may need the money down the road, or someone whose estate is going to charity.

The lifetime limit applies only to gifts above and beyond the $13,000 per recipient rule that allows people to give each year tax-free to any number of recipients [the actual dollar limit changes each year]. For example, if a parent gave a child $50,000 in a given year, only $37,000 would be counted against the lifetime exemption.

Many wealthy people already have given away the old lifetime exemption of $1 million per giver. Now the decision is whether to go ahead and give away another $4 million. And the circumstances are obliging them to think more quickly than they would otherwise.

"If they knew the transfer tax opportunities would be there forever, many clients would defer large wealth transfers," said James H. Cundiff, a partner at McDermott Will & Emery in Chicago.

Indeed, said Edward F. Koren, chair of private wealth service at Holland & Knight in Tampa, Fla., his firm has already talked to a number of clients, or scheduled appointments to talk about how to take advantage of the new ceiling, "even if the amount reverts to $1 million in two years."