Life expectancy of a rim? I've erroneously bought a rim (hoping my technical English is right: the part of the wheel between the spokes and the tire). While I have no immediate use for it, shipping it back to the seller for refund would be a waste of shipping costs if I would need a new rim in the foreseeable future. I have been riding a Gazelle street bike for ~10 years now, and it is showing signs of wear along the periphery. In particular, I've recently discovered I've been negligient with checking the spokes of my rear wheel, which has been running some time with broken spokes. For the second time now in these 10 years.

How long can I reasonably expect rims to last on a street bike? Will I be facing replacements sometime soon?
Rims can last a very very long time. 

The failure mode (other than from accidents) is simply the wearing-down of the brake surfaces over time (see this question). You can literally wear-away the rim surface with your brakes until the rim is too weak. 

Some rims designed for commuters have a groove in them that is designed to indicate wear. When you can no longer see the groove, you know its time to replace the rim (might as well replace the wheel).

Here's an excellent description of rim wear.