I have a 22" Ariens 5.5 Self-propelled, Height-adjustable, Walk Behind Mower/Mulcher w/Electric Start. It's 5 years old and serves me well. None of the parts are plastic. All the gears are metal. Like Henry says, a mower has more to do with whoever is doing the work.
I have 2/3rds of an acre that's 90% hill. Nothing serious but ist's NOT flat to say the least! A rider mower would have been over-kill. A push mower was out of the question. So, I got a mower with a respectively wide cutting area that 'helps' me (self-propell) do the work. It takes me about 45 minutes or less to do the job. My mower mulches and bags. I mulch because, unlike Henry (or his wonderful kids) ;-), I do it every 7 to 10 days. If I let it go too long, it stays damp and is hard to mulch. (The grass height wouldn't matter too much if I was bagging.) 5 years ago, I decided to spend good $$$ for a durable mower. Craftsman mowers are cheap IMHO. Their parts are plastic AND you can only for the most part get parts from Sears! In fact, my neighbor spent $250 for a Craftsman so-called self-propelled walk behind mower and in 2 years, it was shot! I spent about $700 for mine and it runs great and has had no problems. My neighbor, well, he's on his 3rd, yes 3rd mower in 5 years!!!
Like Henry, I do the Fall maintenance. (Replace the oil, drain the gas, clean the gears, spark plug, and filter.) I do the same with my Echo Direct Drive Weed Wacker (straight shaft). This maintenance, like with your car, your heater, and the like, is very important if you want to extend the life of what you own. I know $700 sounds like a lot of $$$ but that's the reason I take care of it! It cost me a lot of $$$!!! So, when the season starts, there's a clean, fresh mower ready to go, and about after 15 hours of running, I change the oil, clean the filter, and wire-brush the plug. All these things are easy once you do it a few times. (TIP: Put the owner's manual in an envelope in your shed and Tack it to the wall.) I mulch my leaves as much as possible and weed-and-feed 2x's per growing season.
There's not much else to say except that whatever you decide to spend, you get what you pay for. My $.02 says to look into Ariens, or any other non-home-center mower. (I'll probably get some grief for this recommendation.) If you're wondering how I chose Ariens ... I asked a few landscapers on my way home from work 5 years ago and asked why they used Ariens. They said they're reliable, durable, take a beating, and easy to fix in the field. These guys are EVERYWHERE! Go ahead and ask them! My best to ya and hope this helps.