Like other PPs, my organization doesn't have an issue with this if it's at the end of the conference and I don't expense anything on my time off, obviously.

Once, my return travel was slightly more expensive than my original flight and I offered to pay the difference and was told it wasn't significant to worry about. That said, any change fees, upgrades, whatever, I paid for myself, of course, and didn't even approach that with my boss.

I do this all the time. Sometimes you can drop the fare for a Saturday night stay, too.

I do it all the time. Since we buy full-fare business class tickets anyway, I use my amex platinum and just get my wife a seat with me on a 2 for 1 business fare. Works great.

We do it all the time. The only thing I do is compare the cost of my airfare - i.e., if I return immediately after the conference, versus if I return a couple days later. If the latter is significantly more expensive, then I pay the difference myself. Sometimes, it winds up actually cheaper, which I figure is a win for my organization!

I work in federal government agency, everyone does it all the time.
simply get pre-approval, and keep the extension a day or two (weekend or AL). Don't make an entire vacation out of it.

Fed employee here - I've tacked Annual Leave days onto work trips to San Diego, San Francisco, Denver, Boston, etc. Sweet perk. I probably would have never travelled to those places on my own expense.

No. They would be paying for my roundtrip airfare anyway, and of course I pay for my own accomodations during the non-work portion of the trip. If you have the available vacation time and there are no conflicts at work, I can't possibly imagine why this would be an issue.

OP,

Ask your supervisor. It works in lots of workplaces. I hope for you!