I propogate them right away. it doesn't matter at all.

I'm confused by your question. You mean you want to cut off stems and root them? What would be a reason to wait to do that?
Sorry for not understanding what you mean.

When I buy plants like impatiens and begonias in the spring, I usually cut them back right away. By cutting them back I get bushier plants. I root the cuttings and as a bonus I get more then double the plants I started with.
To all those new to taking cuttings I would recommend doing a search on this forum for Pinching & Poking annuals, there are pictures of how to take a cutting. I think that might be the cause of some of the problems that people are having with their cuttings. If you don't take the cutting correctly you wont have success in rooting it.