Aha! The million dollar question your doctor and all the specialists in the world can't (won't) answer.. but to be fair it depends a lot on the factors involved: age, health, time to get to operation from the dissection, type of repair: was the heart valve replaced - if so with what type of valve..mechanical or graft..
My event happened in April 2003 and now, 6 years on apart from the usual stuff that you inherit with a mechanical heart valve - (clicking and whooshing and slight circulation problems and taking warfarin every day - and it's implications with other drugs and foods) - I'm a happy camper as just passed my yearly checkup with flying colours!
Oh. Of course. How long? Life expectancy once past the first year or so with all things going well can be as long as 25 years plus! But- life expectancy is not about how long you live - but about what you do with it! Carpe Diem!