I've known addicts who could function, some for several years - until they couldn't anymore. There are far more healthier ways to get a break from work. Oxy's are EXTREMELY addictive, expensive (from what I hear), and not to mention...illegal when used like he is.
You may want to read some of the posts here and on the substance abuse forum and think about if you really want to go down this path with him. I hope not, for your sake. I am a recovering addict, and I hope I NEVER volunteer to get in a relationship again with anyone who uses drugs/alcohol to "escape" life.
Oh, and welcome to SR!
Hugs and prayers!
Amy