What is the typical lifespan of a set of clincher wheel rims? I know there are a lot of variables, but roughly? To be specific I am looking at a set of Mavic Open Pro rims with 2000 miles on them. I don't have them in person so I cannot judge the wear of the break surface.
Short answer: there is no typical lifespan.
The only way to know when your rims have exceeded their lifespan is by inspection.
Why? The wear on a rim is going to be due to a variety of sources: the miles, abrasion of the braking surfaces, corrosion, crashes, plus more.
Ignoring carbon, all respectable rims are made of aluminum, which does have a finite life, as aluminum does not have a fatigue limit. However, that fatigue limit could be reached at 1000 or 1 million miles, depending on the cross sectional shape of the rim and how heavy its loaded. Only way to know, is to inspect.
As for the brake track and corrosion, riding around exclusively with clear skies in the summertime of California will have a much different impact on the rims and spokes than someone riding year round in Minnesota in the sand. Getting sand and other gunk caught in the brake pads can wear the tracks significantly more than in clean situations. Road salt and other substances can corrode the spokes and cause wheel failure through that.
In short, 2000 miles is not a lot of miles except for perhaps super-niche-crazy-expensive-pro-racer wheels that are only used for a few rides before being discarded. For the rest of us, 2000 is barely a drop in the bucket of what a good wheelset will be capable of delivering provided it is well cared for.