This article is from the FAQ, by with numerous contributions by others.
There is NO guaranteed way a person can retain their green card,
unless their permanent residence is IN FACT in the U.S. It is
erroneous to think that so long as you keep visiting U.S. every year,
you may retain the GC. Absolutely not true. As a matter of practice,
INS may not catch you, but they can place you in exclusion proceedings
(sort of the first step in canceling a GC when a GC holder is trying to
enter the U.S.) when they do suspect that you are actually not living in
If a GC holder is planning to be away from U.S. for an extended
period of time, it is best to seek permission from the INS in the
form of "Reentry Permit" (Form I-131). Even this does not
"Guarantee" retention of a GC, but it may be the safest thing under
Because losing a green card is a serious matter, I strongly advise that
you seek the guidance of competent counsel for you individual case.