I went on extended hiatus a couple of times and lost my entire audience. It wasn't a planned thing, I was doing my Masters degree (Modern English Literature - I wrote my dissertation on Watchmen
) and I'd just gotten out of a bad relationship into an even worse rebound relationship. Still, I didn't update for a couple of months, restarted on a sporadic update schedule, and then stopped for another couple of months. I now have an fairly common to me, but otherwise unusual reaction when people find my strip - "Holy shit Neko the Kitty's updating again! Awesome!" I really should advertise to that.
Oh wait, Rob was referring to the recent break. I take a week off about twice a year and it's never hurt me too badly. I recently did a guest week to break up acts 1 and 2 of the current batch of storylines I'm doing, and that worked out pretty well. Got a couple of new readers from the guest authors' audiences, and used the time to set up a fancier site. It's good to take a break once in a while, you don't want to burn out.
Here's a doodly comic I ran for a week when I lost all my art programs last year. I now keep drawing that character in the background as a 'where's Waldo' because my best friend and occasional co-writer McJefferstein hates him.
Basically as long as there's something new on the site, and they're not too long or too frequent, you can get away with taking breaks.
Personally I'd recommend cutting down on your update schedule. If you're eating into your buffer more than you're comfortable with, then that indicates that your update schedule exceeds your work capacity, and you'll burn out quick if that's the case. Try cutting down to a four update a week schedule for a while. That's still more 'on' days than 'off' days in a week, so if you upped it because you felt the 3-weekly thing was too little then that's still 'lots'. Check your stats to see which day has the lowest traffic (it's probably friday) and post a notification saying you'll be putting up one less update a week because you just can't work that fast. Your art's really good, so 5x weekly is simply an astonishing output, people will understand if you can't keep the pace up indefinitely.