I just used my 2 Trakdots on a 15-hour trip from IAD to Montpellier and both worked fine the whole way. One of them (my older one) consistently seems to connect to the network much faster than the other, but they both ultimately do connect and let me know where my bags are (so far always where I hoped they would be.
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Battery life has not been a problem for either one of them - even when I sometimes forget to turn them off promptly.