I used to build wheels (for a "living") and strong wheel takes a long time to build... 3 rounds of stress-relief, even and proper tension, true, dish, repeat. I've never met a bike shop employee who understood wheels worth a damn. The people who build them at the factories usually do a sloppy job too... even on $3k wheelsets.
A properly built wheel should stay true until the rim is bent or broken. There is no way to fix a bent rim, it needs to be replaced... since truing it can only be achieved with uneven tension, which makes it weak. Unlike caliper brakes though, disc wheels don't need to be as true.
A quick and dirty way to check is to pluck all the spokes. Each side will be different but all the spokes on a side should have the same tone.