I am so happy for you and for him that he has made this effort and I pray he can stay on the good path.
Meth takes a long time to heal from and rid from the system, many rehabs recommend long term programs for meth addicts because it takes longer for the brain to stabilize than with many other drugs.
That said, the success of any addict to become clean and stay clean is often directly related to their willingness to do what needs to be done to get there. Some can just stop and never use again, I pray your husband is one of those lucky (and hardworking) people.
Enjoy your vacation, enjoy each day and I hope you will both have happier and healthier days ahead.
Hugs