It's not that hard. Just don't leave the country. Lay low, draw no attention and hope to avoid those random checks. You can last years that way.
Its not the first time I've heard about 10+ years of overstay. The words are that they start out with just a limited time of overstay, for numerous reasons. Then the time flies, they get away with it, and they think it is just too late to fix in a sivil way. They might be a bit embarrassed too, choosing not to think about it, and just hope for the best.
The moral side of it, well that's another thing.