It's possible the spoke tension is out of balance (this can happen to all wheels), which will tend to keep throwing them out of true. A good wheel tech should have a tension gauge so they can ensure the wheel is evenly tensioned.
As far as wear goes, many Mavic rims have internal wear indicators. This are small notches machined on the inside of the rim walls. When the rim reaches its wear limit, these indicators will appear as holes in the braking surface. From memory, I think they're near the valve, although they could be at 90 degrees around. They won't be opposite, 'cos that's where the rim is joined.
Just ride the bloody thing and enjoy yourself!