View last edited instead of published date in dashboard for posts

I have a blog with about 40 posts in one particular category that relate to recurring events. Every four months I go in and update all the posts with some new information to make them show up for another four months in the event calendar 3 plugin I’m using.
What would help to make sure I don’t miss any, is if I could view the ‘last edited’ date in the post from the dashboard.

I’ve dismissed the following options:
1) viewing the RSS feed directly, which shows the information I need to see. It only shows the last 15 posts, so is no good for older ones, and I can’t find anything to force it to show more… Anyone know a way to force a particular category’s rss feed to show all the items in that category, rather than the most recent? I seem to recall it used to do this…
2) Customizing the archive page for that category to show the last modified date or the event calendar schedule. I know how to do this, but I need the archive page for that category to display a certain way already. Is there any way to make a second archive page for a particular category?
3) changing the publish date of the post every time I update. I can’t do this because it changes the URL (drat) and I need people I’ve sent links to to still be able to follow them. I’m using custom permalinks.

What I need is a way to iether get around one of the blocks above, or find another way to see at a glance which items in this category are getting stale and need a refresh. The blog itself has hundreds of entries, so I also need to see it by category, not all the items.

Thanks for your help,
Sophia