Adam, I think this is an excellent thread, and very timely. I too find this issue to be one of the most frustrating and time consuming parts of this whole biz. This year, I'm really looking hard, and cutting out whatever I can. And by the way, I currently only park, although I have had offers to develop some of these which I make take up in the future.
There are some important macroeconomic issues to consider. Internet advertising is growing extremely fast in both scope and rates. Thus, if I have a domain with good traffic and revenue that covers the reg fee, I'm keeping it and regging it out a few years. But the key here is good traffic. If it got hit twice a month with a 2 clicks over the course of a year for a few bucks each, I'm dropping it. Which brings me to the next point...
Domain reg fees are rising. Verisign got a 7% annual increase going forward, not just this year. And it looks like the registrars are going to up the rates on the other extensions as well. So holding costs are going to go up. I'm getting rid of low traffic stuff which doesn't have a clear development potential or broad buyer appeal. Even one word dictionary .coms. I look back and they're picked up, which I find frustrating. I guess there are lots of people who think just because it is a dictionary .com it must have value. But if it's the plural negative version of a nebulous root term which never gets searched, I can't see paying 10 years of increasing reg fees just because a buyer might show up one day. Am I wrong?
I still reg new concepts and see if they work, even if the event in mind is a few years out. But I believe the time for holding huge portfolios that aren't producing income is over. I think you're time is much better spent working on fewer, better names.
-SoCalBoy