Pat, I have the generic Walgreens version of MiraLAX. It's called "SmoothLAX." Like MiraLAX, its active ingredient is Polyethylene Glycol 3350. Under the directions for adults, one of the bullet points reads, "Use no more than 7 days." I know a number have described taking this for many weeks or months even. I myself have been on it for several weeks.
I just find it interesting the discrepancy between the manufacturer's instructions and the advice of a physician, especially when combined with real life AF sufferers. I'm wondering why the manufacturer has that notice. I'm also wondering if the genuine name brand stuff, or even other generics also share that warning.
A couple of interesting side notes. Last year, when I had my colonoscopy, I was prescribed a jug of this stuff with instructions to make up the gallon sized solution, add some flavor, and then drink the gallon over the period of several hours. I didn't think I was ever going to get off the toilet. In the end, it was just kool-aid colored water all over the place.
Also, a substance with a similar sounding name is considerablly more dangerous. Don't confuse them. The other substance is known asc Ethylene Glycol, more commonly referred to as permanent Anti-Freeze.