If the belt is like standard belt drives (I need to look further into this, not sure if Ikea cheaped out or not), it should actually stand up to time better than a chain would. Belts are simply carbon cord embedded in a molded casing of nylon and polyurethane, and, more importantly, do not have any moving parts or linkages. It's just a belt! So you don't have to worry about the metal pitting over time or road salt settling in and destroying your drivetrain like you would with a traditional metal chain. This is more important to the European market where bicycle riders my not have cars, but owning a bike that you aren't afraid of taking out in the rain is another benefit of the belt.

My biggest concern though is that like all parts, the belt will fail eventually. A quick look online shows that new belts cost around $250, over half of the retail price of this bike!

Someone mentioned it is a "conti-drive system". Which iirc is one of Continental's belts. Continental is well regarded in the cycling community for making high quality quality kevlar-core tires that withstand a lot of abuse (gator skins) so I'd imagine their belts are fairly good as well.

...which is presumably why there's a 10 year warranty on the belt.

Nice, good looking out. I assume Ikea isn't about to staff a mechanic for a low-occurance problem for a single product, so I wonder how they will handle warranty for the labor of replacing it.

probably contracts with local bike shops

For a city bike, you could get a chain drive fixie which barely wears at all and only requires some oil every few months, can be repaired easily and is very cheap. Belts last about as long or less as a fixie chain drive with regular oiling.

Belt with two internal gears lasts much longer than a mountain bike 18 speed chain drive, but then you're comparing apples and oranges.

This is a bike designed for the Apple user, basically, except that it seems inexpensive, which is nice. If you never want to think about how a bike works, this seems fine. But my original point was to learn how to maintain a bike.

What makes you say the frame is less durable?

It says that the frame is powder coated. Powder coating tends to last a lot longer and survive more abuse than paint does. Also its a aluminum frame so it is not going to be rusting either.

Because aluminum is literally less durable than steel alloys, and steel chains are way more durable than belts, with a single speed bike.

If you leave your bike out in the elements and don't maintain it, any parts that do not survive prolonged exposure to heat cycle, water, oxidation, salt, etc will deteriorate. But that isn't even metal durability, that's just plain weather. Any bike will deteriorate outside.

Another downside is aluminum is stiffer than steel, making for a rougher ride unless you add suspension, get softer tires or significantly change geometry.

25 year warranty on the frame