Honestly, I equate this to checkups with your doctor. Sure, while you may feel fine, it's a GOOD IDEA to go visit. It's preventive maintenance for your body.
If people want to speculate how long they can go without changing their filter that's fine, it's their choice. But as to whether or not that is a good idea to not change it, I would have to disagree.
I understood this thread to be about whether the filter change is necessary. Ultimately, you wont know until the engine fails from not changing it, or until you decide to get rid of the vehicle, before you can make that determination (after the fact) as to whether it actually was necessary. Either way the engine may or may not survive, but this is a case by case scenario. I say that because while most engines should have it changed, you could have the one engine that goes its whole life without a problem. That doesn't mean that 'IN GENERAL' you should not change it, what it means is that according to probability and statistics, you got lucky.
Then again, most people don't run their engines the whole life without changing the filter. Otherwise we would have a larger sample size of success cases where this was done and proven to not be the issue that most agree exists.