I partly really like the expression / turn of phrase "And so on and so forth". It means roughly speaking something like "etc etc" but slightly cleverer because it demands of the listener to extrapolate based on what you just said and imagine similar examples.
It’s good because it can save time when you are talking about something quite complex, time you can use to build up important ideas rather than laboriously be going over examples. When it’s used well, it is saying to the other person, "I know you know what I mean, you are a smart person, I'm not going to bother you with unnecessary explanations". If it’s used sparingly and respectfully it can be very effective at keeping the conversation moving forward.
Having said that, there is the danger of over-use, of using it as a crutch, a way to be lazy, asking the listener to do your job for you. These are not respectful ways to use this expression.
Anyway, I'm writting about it here so that I remember to use it sometimes. My impression is that I rarely use it. I think if used correctly it can make you sound quite smart. #