Okidoke, usually when people say they have an acre or more on here, they are slashing thick 2ft high weeds every mow.
If you have been using that for 20 years, and its still in that condition, you obviously keep up on the mowing regularly - well done.
I personally couldn't do it due to health issues, but it must keep you fit.
Any americans reading this will have a heart attack - most get ride ons for 1/4 acre blocks and push mowers dont come smaller than 21in over there