samshine:I never switch the tags. We have an every day collar where the tags stay permanently. When we get to training class we switch to which ever collar is appropriate. I've never felt that my dogs need to have their tags on when training, and I don't think anybody else worries about it either. In fact, when you show in AKC the dogs are not allowed to have any tags on while in the ring.
I train on public sidewalks, in stores, and in public parks and the dogs are required to be tagged and licensed with the county or you get steep fines b/c those are public locations. Also at both training clubs I belong to, we train outdoors in rural areas and it wouldn't be the first time a dog spooked for whatever reason and got away. It has never happened (or come close to happening), but never say never
Different test also require different colors (no tags, but it still means possibly taking tags off the collar). For example for TDI I had to have a flat buckle, for TT we have to have a choke, etc.
My Blog - http://24ft.dutchbingo.net
My Site - http://liesrosema.com