What things are acceptable to ask your SO to change? What things are not?

So, ever since I asked my question about my boyfriend’s cologne, I’ve been wondering where the line is between things that you can ask someone to change and things you cannot, reasonably.

Generally, after spending a certain amount of time with a person, there is something that irks you. Is there a level of commitment you should have to someone before you can ask them to change this?

What things are completely off limits for you? Have you ever broken it off with someone because they wouldn’t change something? Or, the opposite, have you ever ended a relationship because the other person asked you to change?