Purchase Products With Common Parts
Dependable appliances are popular appliances. The more popular a particular model, the more likely it is that replacement parts will be available when the time comes for a repair. And the more common those parts are, the greater the chance that you can buy them quickly and affordably when you need them.
Consider the alternative. When it comes time to replace a belt on the weird, oval-shaped dishwasher that you had imported from a no-name company in the South Pacific? Good luck.
One key point is to make sure you know the exact model number of the appliance you're considering. From there, you can search a site such as RepairClinic.com to see how easy (or how hard) it is to find various components for that dehumidifier. If it looks like parts are scarce, think again about buying that particular model.
You can also take your parts smarts to a higher level by being observant. Take note of the construction materials of the parts in highly-rated products, and keep track of how those parts are assembled. Are you looking at a dishwasher made of nothing but plastic pieces permanently glued in place? Or is it made with more rugged metal parts that can be unscrewed and replaced when necessary?
Those kinds of details are often telling, and they can help you veer away from a disposable product and toward one that's really worth your investment.