dream, i can relate to the images. yes they do eventually start to fade. its up to you how long you will allow yourself to go there in your mind. its not easy but you will get there.
excuses, there will always be excuses as long as they are active. i think its common that he would look clean while on work release, maybe give it some time then you'll know whether or not it will stick. is he working some kind of plan of recovery? something to think about.
my ah would sometime do really well as long as he was monitored by the authorities but when released, he'd go back to using. i pray that your bf will continue to do well, i also pray the same for you.