I think it’s always good to validate. I agree with @bb254 about engineers being trained per the SOP’s of the company and validating equipment. I think every employee, not just engineers should be made aware and trained in the validation process. To answer @tn58 original question about how to understand the validation process, I found flowcharts and checklists very helpful. Specifically, I found this flowchart from (samaras-assoc DOT com/quality DOT htm). It put all the necessary validation checkpoints in a timeline so you could have a better perspective of planning your validation process.
I think if everyone in the company is made aware of the seriousness of the validation process, they will be more wary, in general. Sometimes, there are unexpected issues that may not require a validation process but would benefit a lot from having one, then it’s a good thing to do.