suppose you were snatched up by (insert prefered deity here) and given a choice:

two boxes are placed in front of you... choose the box on the left, and you are guaranteed a moderately happy, fairly consistant life... youll never be HUGELY happy, but then youll never really face despair either... there will be ups and downs but all of them minor... all in all a better than average but completely unremarkable life...

on the other hand, you could choose the box on the right... this box comes with only one guarantee: that the life within will start out EXTREMELY happy... but there is a 75% chance that at some unknown and unpredictable time in the future, your life will take a nose dive straight down into abject, soul-sucking misery. to keep things interesting, this life will also have its fluctuations in quality, and they will tend to be larger than the more stable life in box A, but on the up-side the positive swings will get you as close to bliss as youre likely to ever achieve... the down-side being, once it takes the true nose-dive, thats it, its all downhill from there, and you wont realize its more than just a negative fluctuation until its well on its way down...

as an added wrinkle, the deity tells you it isnt entirely unkind... that if you gamble and choose box B, you can at any time reverse your choice, and trade it in for the life in box A... however, you can only swap once, theres no going back if you do decide to back out... and as an additional penalty to stop you from trying to get the best of both world, youre advised that if you DO switch, youll have to endure the soul-sucking misery for a period equal to one-half the time you spent with the life in box B... in other words, if you pick the great but potentially horrid life and stick with it for 10 years before things really start to suck, you still have to live with the suckage for 5 years before youre allowed to swap to the mostly good but unremarkable life in box A...

how would you choose, and why? what would be the optimal strategy for playing this "game"?