How long is a piece of string?
Yeah, I get it. You don't want to hear that but training a dog with separation anxiety to cope while home alone is not a straight line.
We are trying to fix an emotion, not a behaviour, and this means it does take time.
Would you expect to stop a dog with aggression towards other dogs or humans from acting out in a couple of training sessions? It can take many months before the dog is able to be around other dogs. In many cases, aggression is fear-based and fear is an emotion and emotions take time to modify. It's about creating a mindset shift.
When your dog exhibits panic when you walk out the door, this also is based in fear and we can't just wave a magic wand and wish it away.
In addition, remember that just like us, dogs have good days and bad days. You might achieve an absence of an hour one day and the next day only make it to 5 minutes. So many things can affect our mental state, and indeed our dogs. If they have had a fulfilling fun and enriched day they might rock your 2-hour goal, but if they had an incident at the dog park or a nasty experience at daycare or exposure to something scary, they may fall in a heap during training that day. So it's important to keep this is mind and this is why we always strive for consistency rather than extended duration. It's better to rush slowly then go too fast and fall flat on our faces!
So how long does it take to train a dog with SA? Well, it also depends on the dog!
Some dogs fly through training and others struggle and need additional help and support. Just like us, they are individuals and just like us, they deal with things differently.
The most important thing is to give them the time they need. Let them go at the pace they can cope with and not rush them too soon.
This is essentially the key to successful training.