It was in the 60s, maybe 63 tabs? Firefox 30 on Win8. Amazingly (not!!!) it crashed. FF crashes every day for me. Unless I crash it myself in Task Mgr first. I typically have no fewer than 30 tabs open. Can't get FF to run 24 hrs without burning 2 gigs of memory. It leaks like a sieve. I typically have several Twitter tabs, a couple LinkedIns, one Gmail, Blogger and Wordpress (a couple each), Google Finance, Hacker News, and miscellaneous articles/blogs open, plus Mailchimp and Hushmail. Lots of AJAX-intensive pages and Flash pages (Google Finance, for example). No porn.
Sometimes Flash will complain, but most of the time FF just runs out of memory and starts giving the spinning cursor. Once in a while it will crash without bringing up the crash reporter window. It'll just go down silently.