How long should appliances last?

I have a blender that's at least 20 years old. Recently, the black base that holds the glass jar cracked and I was faced with buying a replacement part, or getting rid of the entire machine and buying a new blender.

I like to consider myself a 'green' consumer, so I went online to find replacement parts. I found one at a decent price, but with shipping and handling, the cost almost doubled. So then I wondered whether it would be more cost-effective to buy a new one. Would it last longer? What if the motor wore out on this one right after I replaced the broken piece?

I hemmed and hawed- and have done nothing. Paralyzed with indecision. This happens with me and appliances.

In the last year, these items have stopped working properly at our house:

Black & Decker weed-whacker (Electric grass trimmer), 8 years old: Despite repeated charging, it would not hold charge for more than about 5 minutes. Had to buy a new one.

Panasonic microwave, 12 years old: LED display does not surface properly- but I can still get it to work. Replace?

Rowenta iron, 9 years old: Light turned on, then immediately turned off. Would not heat up. Worth it to ship to a Rowenta dealer to diagnose? No, I bought a new one. A cheaper brand.

Here's a guide to appliance shelf life at appliance.net.

Here is another guide at Old House Web.

My fellow blogger, Kim Palmer, says she runs through one Dustbuster a year. With several animals, it gets worn out.

My one bright spot: Our Salton waffle iron, right, we got as a wedding present 26 years ago. We use it almost every week and it works like a champ. Never have had a problem.