I hope this hasn't already been covered - I couldn't find any earlier discussion. We are heading off to southern France shortly and, because of worries about sand flies, have bought scalibor collars for both dogs. (We also use Advantix which seems to work for tick prevention). It says the collars work for 5-6 months - does that mean we can use them for a month or so now and then take them off , presumably seal them back in their foil envelopes and use them again next spring?? How does one know if they are still working?? Any help greatly appreciated!