I also wonder about people who take in failed guide dogs. Does all that training go out of the window just because they are with a new family? Not from what I’ve seen.
Training needs continual reinforcement to stay around, for the most part. The extent to which this happens will vary massively, according to the strength of the lesson to start with, the individual dog, the environment s/he then lives in and what counter reinforcement is happening (accidentally or otherwise).
But yes, if you take a dog and teach it to bring you a sock (e.g only) then send it to a house where sock bringing is no longer practiced or reinforced then the sock bringing will eventually be forgotten.
If that dog gets the sock training for a day, it is most likely going to forget it quickly.
If that dog spends 5 years being trained to bring a sock, then it is likely to take years to forget it.
If that dog is trained to bring a sock but in his new home, he is punished (even accidentally) for bringing that sock, he is likely to learn not to bring socks.
Apply that to recall:
- in a new environment with a new trainer the dog learns that coming when called is rewarded.
- he goes home and the owners use the same command but never reward it; the learning is forgotten
- he goes home and the owners remember to reward for the first few weeks but then stop; it takes a bit longer but the learning is forgotten
- he goes home and recall is only ever used to signal the end of a walk (e.g. accidental punishment); the dog learns not to recall
There will be exceptions to that but the fundamental principles of learning mean they are the most likely options.
Training is different to personality shaping. A dog brought up to be settled and steady is likely to keep that personality. Especially if they have also been selectively bred to have those traits - as guide dogs are.
Oh, and guide dogs that are successful go to owners that are taught all this - and that commit to doing the maintenance required to keep training fresh in the dog's mind. Otherwise, even the successful dogs' training is lost eventually.