The current rally is just a wee bit over eight years, six months old. Any way you slice it, it's an incredible, though still not unprecedented, run since the Dow's low of 6,469.95 on March 6, 2009.
Now that the bull has reached a ripe old age, more and more talking heads are calling for its end on the basis of its "advanced" age alone.
I'll be blunt: Changing your bullish bias and acting on the assumption that the simple passage of time is enough to halt the rally is likely to cost you money - and plenty of it.
I can say that with confidence (and trade likewise) because, over my 31 years in the markets, I've learned exactly what ignites, what perpetuates, and, of course, what kills, a bull market.