I need to find a way to reduce my queue and 'lesson the load'. For more than a full year I've put in at least half an hour a day into Skritter--and achieved great results. But now that I know more words, there are more and more reviews to do. Lately, I've been averaging maybe 45 minutes a day just getting my queue to zero, without adding many new words.
1) I need a bit of a break;
2) I worry that at this rate, Skrittering won't be sustainable as life changes, new priorities emerge, etc.

So my strategy for the time being is to stop adding new lists (I just finished off HSK 4, which seems to be a good place to take a breather) and new words. My hope is that if I answer "Too easy" on enough of my queue, I will gradually reduce my queue and thus the amount of time it requires per day. Will this work? Any other words of advice?

My goal and situation is somewhat similar. I have not added any new words for about a month except the occasional word that I find when using the char/word pop-up. After this month or 6 weeks I have reached a stable state where my number of reviews is manageable with about 20 to 30 minutes a day and if I miss a day or two the queue isn't forbiddingly large. It is sustainable.

I am focusing on conversation skills now rather than adding to vocabulary while using skritter to maintain my reading and writing and I am satisfied with this plan.

You suggested grading with "too easy" which I have done on many words but only those that are indeed quite familiar. I find that a few words come up after long periods (2 to 3 months) that I have indeed forgotten. Those get marked wrong, get reviewed in a relatively short time and I remember them after just one review or two and they're back to longer review cycles. (At first I marked them a "so-so" for fear of adding to my review queue but that was a mistake.) The system works in that I get occasional reviews of everything and the words I forget get more concentrated review.

No adding for a while will help. You can also lower your target retention rate if you want to do less reviews. It'll take a good while to propagate through, but eventually the load will go down even more if you do.

Generally, though, if you stop adding, your review queue will naturally shrink. You can also get your reviews due a little past zero each day, doing some overpracticing, and that will help clear out some of your longer-term reviews in advance. Then less are "due" each day, which can be psychologically more reassuring.