Make on extra mortgage payment a year and pay off in 17 years. How do you do that? I round up a little. So your mortgage payment is $1020. Pay $1100. Like you're going to notice the missing money. But if you take a look - it totally adds up. Faster than you would think.
Anyhow, I have a 15 year and I'm still rounding up to the nearest 100 plus a hundred. It pays off.
Which is another thing - given the economy, try for a 15 year and put at least 20% down to avoid the dreaded "mortgage insurance" which is also a ripoff.