A.F.
Edit: I would also want more information about the lifetime guarantee - is it truly lifetime? Or is it a one-time re-do? Does it include the changes for near/far that cause the need for bifocals? I think the fine print would help me decide...
Original: Depends on your age. Right around 40 (and it's strange how close to 40 that number usually is...) you'll likely need bifocals.
Lasik is not a forever procedure. Your eyes are always changing. They will correct your eyes back to 20/20 or better. Once they start changing again, though, your eyesight will deteriorate again.
I would consider your family history - who do you take after eye-sight wise? How bad are their eyes? How bad are yours right now?
Do you plan on having any more children? Is it even a remote possibility? That will likely change your eyes.
Lots of factors to consider.