C'è un limite di dimensioni per i feed?

Secondo le specifiche no, tuttavia FeedBurner limita il peso del feed a 256k.

Yes. FeedBurner will not accept feeds that are larger than 256K. It's rare for a feed to be larger than 256K, but some publishing tools generate their original source feeds with no limit to how far back in time they will reach to include items. Such feeds are vulnerable to steady size increases.

If you currently publish an existing FeedBurner feed, and the original source feed exceeds the 256K limit, FeedBurner will not update the 'burned' version of your feed until the original drops below the limit. For most feeds this will never be an issue -- but if you know that your content postings are regularly very large in size, you might want to keep any eye on the original feed's file size.

FeedBurner Support: Is there a feed size limit?

Ragionevole come scelta. Il feed è nato come un formato leggero di distribuzione, un feed oltre 256k è una martellata. Voi fate come preferite, io comunque continuo a preferire i feed non full content :) ... con quelli per arrivare a 256k ne devi scrivere di articoli!