Are you sure it's because you're not spending time with him? I don't spend time with the vast majority of my snakes and none of them suddenly become snappy for this reason.
Is he hungry or near shed? Perhaps he's looking for a girl and your presence is unwanted? If he's nearing 18 years+, perhaps he's getting old and starting to slow down?
Snakes are probably one of the best pet for people without a lot of time, as they're quite content to be left to their own devices. If he's as old as you think and you've had him for so long, I personally don't think it's really fair to be putting the stress of a new house on him.
To add to what Iguana said, definitely do your research on the people beforehand. See their home/environment if you can (although some people may be unhappy with this), ascertain that he will be a pet only, etc.