While I have no doubt that dealers (and others with an interest in selling you services) will recommend a valve adjustment, my general rule is to follow the maintenance schedule created by the engineers who designed the car. At 30,000 miles the manual says you should:
The Mirage uses the 3A92 engine while the 6B3 is
used in the Outlander. The 4J1 series is
also used in the Outlander. Perhaps I'm misreading this, but it seems that the recommendation for a valve adjustment at 30,000 miles might be an artifact of Mitsubishi handing out the same maintenance manual for all their cars.