My bottom of the line MTD mower is 14 years old and runs fine, because I take care of my stuff and do necessary repairs. Anybody who pays 3 times as much for a mower with a Briggs & Stratton engine is a fool.
My Murray Quatro lawnmower from Walmart is going on three years. It has a 4HP B&S engine. It cost $139.00. I love it. My lawn is about 8,000 Sq feet, and being in TX, we have a long mowing season.
It's lightweight, starts everytime, and other than changing the airfilter once a year, and the spark plug at that same time, I've had virtually no upkeep on it.