
I've used indigo tags on three dogs, the last two wore them for at least ten years if not longer, current dog has had hers for four years.
I too got fed up with losing the name tags mainly due to the ring gradually wearing away the disk making the hole bigger and bigger until they vanished one day in a field somewhere. Or the they just came off the collar somehow. Never lost the indigo ones, yes expensive, but at least you will know your dog will be carrying I/d.
Having said that, I've been using another tag as well which has a black paw print on it giving my new mobile number and holiday home address and it seems quite a thick disk, I can't remember where I got it from, will need to do a bit of research, but it is still going strong and hasn't tried to come off. I replaced the ring with a much more robust double ring which was originally on a car key ring.