If your partner hasn't come out to his parents about his sexuality or about his relationship with you after fourteen years, he is either fearing facing serious consequences, or has issues with himself about this. I would be EXTREMELY upset if my same-sex partner wouldn't come out to their parents if they weren't serious about the repercussions.

Also that 'let them have their one week of bliss' is a blatant form of self-comforting. They've believed he was straight for his whole life. If he isn't facing physical or severe emotional withdraw threats from his parents, there could be something more at play. Doesn't he think he could talk to them? Are they hard core homophobes?

All in all, I think you should bring up these points in a sit-down, one-on-one talk.