I went on my first backpacking trip in over 5 years this weekend and had an interesting problem with my stove.
We were camped at about 10500 feet and the temp was a balmy 38F. I had tested the stove before we left and, even after 12+ years, it ran like a top. Well after fishing, we came back to cook and the stove barely ran. It did not have the infamous chug that I was used to and took about 40 minutes to boil water. New fuel, too. I was wondering about the altitude or temp, but I didn't think it was either of those. The pump is new, also.

The next morning I primed the stove and it fired right up and boiled our water in no time.

The only theory I have is I may have over filled the bottle (A small MSR bottle) slightly over the fill line and it did not get enough initial pressure? Any thoughs or experience?

Since I have gotten the bug again and am going to spend the winter replacing some gear, what is a good stove for overnight to 4 day trips over 10k feet?

(BTW, the trip was fantastic! I hadn't done it in years and had a great time even if my boots finally gave up 2 miles from the trailhead!)