In 18 months, Phil Heath has the chance to achieve a Mr. Olympia record streak, then retire before his 40th birthday.
I can't see anything upsetting this. Ronnie Coleman won the Mr. Olympia until he was around 41.5 years old [2005]. Phil's physique still looks extremely fresh. Maybe competing once a year is helping to keep his receptors fresh.
I don't see it going any other way, unless Phil doesn't want the above to happen - or has a health scare. But again, competing once a year probably helps him tremendously in that area.