From what I heard from a man who studied physics and astronomy for years (but doesn't keep track anymore to the newest inventions that much), he says that it's close to impossible for a mini black hole to swallow the earth in 15 years.

A mini black hole is so small that, when reaching the center of the earth, the atoms are way too far away for it to suck them up, and will decay for 100% certainty before it sucked enough matter to keep growing (this doesn't mean that it wont ever happen, but percentages can't have a floating point and must be rounded to the nearest round number )

So, I do believe he knows what he is talking about, and it sounds very very logical. I have my answer.