I tend to make lap/throw quilts more than anything else. I think, like many others have already said, it's because it's a manageable size to work with and practical to use. My I Spy quilts are generally 42x54 (I play backing chicken with that width, I know, but have been lucky for the most part). I have made a queen-size double-sided flannel quilt and a king-size quilt and SID quilted them on my Brother PQ1500. I don't think I'd like to try either of those again (even though I was happy with the results) because it's so awkward to work with something that huge/heavy.