32 and currently at 73% equity (wow, I had never worked that out before!!), have been making significant overpayments the whole time. However... we bought the house to renovate it, so when we get to that, overpayments will stop and we will be ploughing all that extra money into the house. I guess our equity will still increase, since we will be gaining 'sweat equity', but our mortgage will remain the same (well, just reduce by the monthly principle) for a few years.
If we didn't do anything to the house, it would be paid off at this rate in 2016 (age 34). If we spend our budgetted amount on it, we could pay it off in 2019 (age 37), assuming our work situation remains the same. If we decide to have kids, all bets are off.