If you poll the main page RSS less frequently than every 2 minutes, you'll miss activity during the busy parts of the day:
I haven't found the "newest questions" RSS (surely there's one there somewhere?) but it appears that there are 30 new questions every 15 minutes, so if you poll it less frequently than every 15 minutes you'll also lose new questions.
- Is polling the RSS this frequently ok for stackoverflow?
- If not, is it published/federated elsewhere, perhaps in RSS feeds with more entries?