It took me about 3-4 years to get most everything back..If he has any saliva then it could be very good...I also noticed a big step change in my mouth with soreness and taste improvement after HBO therapy because of the tooth extraction....I think about late year three. I went from a feeding tube, with several treatments to restretch my esophogaus so I could eat again, no taste of sugar, to tasting chocolate again...So tell him to hang in there with it and be encouraged as things do get much better with time!