MarsEdit 4 added a new feature — the ability to sync all posts. It didn’t work for my Blogger posts, somewhere around post 3,000-4,000 Google Blogger dies. It looks like a Google bug.
It did work for kateva.org/sh though — that has over 30,000 posts (it mirrors my pinboard shares and twitter tweets). Unfortunately that slowed MarsEdit launch severely — it took up to 3-4 minutes to start. Turns out MarsEdit loads all posts into memory and it doesn’t scale to that size.
I reset the kateva.org/sh sync to ‘last 50’ and startup is ok now.