A toaster oven should last a minimum of 3 years to 5 years.
However some toaster ovens may last longer than 3 to 5 years and some toaster ovens may rust out before they actually go bad and quit working.
The lifespan of a toaster oven also includes things such as how often the toaster oven is used, how well care for the toaster oven is and also the quality of the toaster oven.
Regular cleaning of the toaster oven and avoiding damage to the heating elements can help extend the lifespan of the toaster oven.
I have a Kitchen Electrics toaster oven that was given to me by neighbor that was moving and it was 5 years old when he gave it to me 5 years ago.
It's still working 5 years later and the toaster oven is now 10 years old and although the toaster oven does have a bit of rust in the bottom of the toaster oven, the toaster oven still works perfectly.
But I've also had a toaster oven last only 3 years and so it can vary.
The most common failure for toaster ovens is degradation of the heating elements over time and problems with the timer and switches.
Regularly cleaning of your toaster oven to remove any food particles and crumbs and keeping the toaster oven dry can help extend the life of the toaster oven.
Frequent use of the toaster oven, especially when cooking moisture heavy foods can shorten the lifespan of the toaster oven.
And poor wiring and power surges can also damage the toaster oven.
Higher end more expensive toaster ovens tend to last a bit longer than cheaper toaster ovens, although even a more expensive toaster oven can fail prematurely.
Signs that it's time to replace your toaster oven include it's completely stopped working, the cord is damaged, the toaster oven no longer is heating effectively as it used to, the knobs or timers are not working or the glass is cracked.