Refrigerate it, preferably at a temp well above the freezing point. Then it will be fine.
I've had no issues with refrigerated 665 expired by at least a year.
Caveat: there are always issues with outdated polaroid materials, in my experience. With colour polaroid materials this shows up in interesting colour shifts. The only somewhat pesky issue I have seen with refrigerated 55 is that for some odd reason, the end-clip sometimes doesn't reclip on the paper envelope when you put it back in after exposure... perhaps the paper has lost some of its rigidity because it became moist over time or when warmed up. In case that happens, don't panic, just be ready to disassamble the cover of the holder (easy) so that you can help it on through the rollers. It's not the end of the world, just a small nuisance. Because of this spurious issue with older 55, I keep a clearing bath nearby when using it and don't pull the film out without developing it. In other words, I develop as I go.
I have not had any issue with expired, refrigerated 665- the stuff works beautifully for me. Literally not one single problem. It keeps exceptionalyl well, and if anyone (Fuji?) picks up a pos/neg material, I would wish for it to be in "pack film" format, not the single-sheet form which has some intrinsic issues, in my opinion. The convenience of being able to develop later is not as important as getting a good pull each and every time and no hangups, in my opinion. I think Fuji realized this and that's why they make their 4x5 stuff in pack form, not sheets.