I had that mentality when I booked my flight for Christmas of 2004. Going home was RDU → MEM → MLI and coming back was MLI → DTW → CLE → RDU. I thought, “Awesome, more time in the air, and more FF miles!” That was also the year that there was the major ice storm at, oh say, MEM, baggage handlers at PHI took a vacation, and all hell broke loose. Needless to say I was sort of regretting that decision, and while my flight out was cancelled completely, I took a $300 credit on my (very delayed) return trip and instead did a MLI → DTW → RDU. Of course, my new return flight got delayed as well and I got to spend the night in DTW for free.
If you’re doing it in hopes of giving up your seat and getting some sort of voucher it’s the right way to go. If you’re just looking to get home, well, you leave yourself pretty wide open to getting screwed over. If it weren’t significantly more expensive for me to tack on the extra leg I’d probably do it if time wasn’t a concern, but considering I don’t get that much vacation at work I’d rather get where I need to be going than work the system and lose time with my family.