My wife spends some time keeping my Linkedin account active, and I spend about 15 minutes a day maintaining a 'pipeline' spreadsheet and replying to inquiries about opportunities. If something gets to the introductory-call stage, I'll try and space them out so that there's no more than one per day. Generally I find that it takes about 30 days from introduction to closing a deal (sometimes longer). At the moment, I have multiple retainers and my plate is full, so I only do the minimum effort necessary to ensure that there's 4-6 opportunities somewhere in the pipeline, regardless of whether they close or not. Obviously if I weren't eating quite as well, I'd probably put at least double the effort into it.

As far as engagement length, my longest engagement is currently 6 months. Generally I don't have an issue with getting promoted into management as an independent contractor, as my loyalty is ultimately understood to be to my own company, and I make it very clear that I do not wish to become a manager. If those terms aren't acceptable, hey, I'm a contractor, everyone's welcome to terminate the relationship with zero hard feelings whatsoever, which is both an advantage in the current economic environment as well as the reason I need to maintain a pipeline of opportunities no matter how well things are going.