I love that you're not combative. Thank you for being polite.
I don't run "unsafe" or mega-doses. This would diminish B12 levels in your system and even prevent absorption. I also test my pH (potential hydrogen) levels every Sunday. At 500 to 1000mg my pH levels are steadily balanced. When I go over this dose it throws my levels off. At even higher doses it's way off and I backed off quickly because that indicates that my body is headed towards lactic acidosis -- not good. This and a host of other issues are very easily overlooked because they're too detailed for most folks to look into and often misdiagnosed. Anyway...
I run 500mg every night to balance blood sugar, improve cellular immunity, manage cholesterol and for it's cardiovascular improvements. It can prevent heart attacks or strokes.
Apoptosis is the process where your body automatically kills cancer cells. Metformin 'boosts' Apoptosis so it can prevent cancer and even shrink tumors.
At my doses, Metformin is a 'caloric restriction mimetic' and for that reason I have no doubt it can extend one's lifespan. I've lowered my triglycerides back into range with it. There's a whole lot more that comes with Metformin so it's certainly one of my preferred prescriptions.