Article limit in Pro. What should it be?

For technical reasons, I have to impose an article limit in Instapaper Pro 1.4 in addition to the new limit in Free. The iPhone doesn’t have enough horsepower and memory to hold more than a few hundred articles without massive complexity (and slowdowns) to load and unload subsets of them as you scroll.

People are using Instapaper in ways I had never envisioned, storing thousands of unread articles. I got a very nice support email earlier this week from someone saying that the Unread page wasn’t working, and he suggested that it might have been because he had 16,000 unread articles. (He was right.) I never anticipated this sort of scale – the most I’ve ever had unread was 72.

I imposed a limit on the Unread page to fix this: it now displays a maximum of “only” your 500 most recent articles.

I also get occasional reports from users that the iPhone apps crash or perform badly for accounts with hundreds or thousands of unread articles. I’ve improved the storage and performance for 1.4 to alleviate some of these issues, but ultimately, I believe this is an edge case: if you’re accumulating thousands of unread articles, are you really going to scroll through the unsorted list to find number 1,628?

So I need limits. For Instapaper Pro, I was thinking of a limit of 250. Would that be sufficient? I feel that it’s still a bit high for performance and stability, but I don’t want to frustrate Pro users if they really want that many. What limit would you propose?