Right now we have 4 months...working on getting it up to 6. We don't touch this money unless all other resources have been tapped out. DH's job is very secure and we pretty much only count on his salary when budgeting, planning etc. My job is decent, but it comes w/ a lot of unpaid time off (which I love!) but no paycheck is ever the same - so we never "count on" my income. We also have a smaller "e-fund" where we throw monetary gifts, bonuses, rebate checks from things we've purchased, and then any extra cash we can. We use this for unexpected house repairs, replacing appliances or other big ticket items, and if we get it built up enough we may take some money and put it towards something fun (we're taking a mini-vacation to the beach soon).
I've come to realize that everyone's circumstances are different and what may work for one person may not work for another. Some people aren't savers, while others are extreme penny pinchers. At the end of the day you have to be comfortable with how you've prepared for the unexpected.