I bought 4 to take me up to the end of March when I will fingers crossed be at target- it is too good an offer to pass up. Just be mindful of the use by dates - most of the powder packs have a use by of september 2010 in my boxes - but the bars were shorter, can't remember off the top of my head but perhaps you could check with Exante what the use by date is likely to be before deciding how many boxes to buy.
Good luck with the journey Arwen.
x