Bought these a month ago for a recent holiday- they were comfortable despite a fair amount of walking. However, I did find that the 'Birkenstock' on the inner side of the strap faded and rubbed off, which after just a couple of weeks was disappointing.
Unfortunately, I lost the right sandal between a train and the train platform as it slipped off whilst I tried to negotiate a suitcase on board post holiday. So alas, i've not enjoyed the long term investment many do with Birks!