The laws have been changed several times over the last year in French Polynesia and it has been causing some confusion. Here is the story as we know it:
First you must separate customs from immigration in your mind. When you fly into an international port you usually clear passport control, then pick up your baggage and clear your baggage. The passport control is immigration and their laws deal with how long your body can be in their country depending on which country you are a citizen of. Then you clear customs and their laws deal with your baggage, your stuff.
This is the same with French Polynesia. There are immigration laws about how long your body can be here and laws about how long your stuff (your boat) can be here. For Americans and Canadians, your body can be here 3 months out of 6 months. This used to mean that you could be here (in French Poly) for 3 months, then get a renewal for another 3, totaling 6 months in 12 months. However, a number of years ago this changed and after being here for 3 months, now your body must leave French Poly for 3 months before it can come back for the second three months.
As of Dec 1998 (Arrete #1861) their was a special customs law for non-resident boats (not the boaters' bodies, just the boaters' boat) visiting French Polynesia. This law stated that visiting boats, of non-residents, could stay in French Poly for 24 months without paying taxes and that time on the hard at a boatyard, with the person out of country, if properly documented, did not count toward that 24 months. Also, with this law it wasn't clear how you could reset the 24 months but it seemed that simply taking the boat out of the country, clearing it in and out of another country, and returning would suffice.
The problem was that there is another law, an immigration law, on the books which says that after 6 months of living in French Polynesia, you are a resident.
In mid-2012 the customs officials suddenly started enforcing the customs law differently. They said that because immigration considered anyone inside the country for 6 months a resident, that any visiting boaters here for more than 6 months were residents and because they were residents the special customs law no longer applied. Several boats were fined and ordered to leave or pay the tax (approx. 26% of assessed boat value, called Papeetization). This new interpretation caused a big stink.
In March of 2013 the stink was semi-resolved with a new law (Arrete #401) which established that visiting boats, of non-residents, could stay in French Polynesia for 18 months, consecutive, time on the hard doesn't mean anything, and the boat has to be out of the country for 6 months to reset the clock. When this law changed, some boaters mistakenly thought this meant their bodies could be in French Polynesia for 18 months even though this was a customs law not an immigration law.
While this new law is clearer on many fronts, it still didn't resolve the issue of residency. However, at this point, customs is going back to their old policy of ignoring the residency law and so boaters can (for now) ignore it as well.
Further, people already in country have been scrambling to find out if they are on the old law, the new law, or a mix, and this has been being solved on a case-by-case basis rather than a straight grandfathering.
Finally, the boatyards, which used to make good money off people leaving their boats here to extend their 24 months, are not happy with the new law.
Several different organizations including the association of local cruising vessels are pushing for changes to this law and I wouldn't be surprised if we have to write a new update in the next year :)