Research Trips -- When?

[rj_anderson]

So let's say that you are writing a book set in some faraway and unfamiliar location, and you are seriously considering taking a trip over to said exotic locale for the purposes of research. You have approximately twelve months before the book is due in to your editor. (You also have three young children and a husband whose work has intensely busy seasons in April-May and September-October, but we'll try not to overcomplicate things.) At what point in the writing process would it be best to plan said trip? I put it to you in the form of a poll:

[Poll #1158658]
I would especially value the input of fellow authors who have recently done this kind of thing -- did you wish you'd gone earlier in the process? Later? Any other words of wisdom to impart about research trips and what to do or not do when embarking on one?

X-posted from fangs_fur_fey.

ETA: dichroic asked where this faraway, exotic location might be -- for my purposes I'd be looking at parts of Kent, London, and the Cardigan Bay area of Wales.