Hey guys -- I went awol for a month and have about 320 cards due (of ~550). Should I redo them in one sitting or am I setting myself up for 320 cards due in one day down the road somewhere?

The scheduling algorithm does a 33% plus or minus so I don't think you would get them all at the same time. So, let's say you have 100 that are going into the 30 day pile. You'll probably get 5 of those a day for 20 days, in the range of 20-40 days in the future. If you put 100 into the 3 day pile, you'll get ~33 in 2 days, ~33 in 3 days, and ~33 in 4 days.

edit: haha, I love your kanji avatar. I made that my symbol on twitter for a little while.

Ah, thanks sir ^_^

About the kanji: one of its readings is phonetically my name >_>...

a month and only 300 reviews? Sounds like you're taking it easy How long does it take you to get through 100 reviews? You could knock that many out in one big session or break it up into a few. Best thing to do is just get it over and done with.

Is this over the website or something like Anki?

With Anki, when I get backed up, I like to isolate my cards. I try to work on the most recently due cards and the ones with the highest ease first, with the rest of the due cards suspended. Then I slowly unsuspend more cards as I reduce my stack. This usually takes me a couple days, depending on how many facts I've built up. This seems to flow better for me at least.