The default on the Janome is 1.8 which is too small if I have to unpick, so I bump it up to 2.1. That is small enough for the stitches not to come loose but large enough to pick out easily.

My Janome defaults at 2.4 which seems pretty big, so I try to always go down to 2.0. Sometimes I forget. Going smaller is only in the last year and so far none of my earlier quilts have come apart so I'm not sure what difference it makes but over more time, it may.

I like 1.5 for paper piecing (easier to rip off the paper). For other piecing, it varies between 1.5 (unsure of fabric quality, know the seam will be cut later, or know the fabric likes to fray), 1.8 (default for stitching with my quarter inch foot on my Janome), and 2/2.4 (I was sewing clothing and forgot to change it).

Thanks, everyone - I think based on the responses here and knowing the power of a collective multiple lifetimes of experience, I might have to bring my length down a bit. :-) As some have mentioned, I haven't really run into issues but perhaps over the long term it might make a difference. I do appreciate all of the answers!

If you wish to continue with a larger stitch length, you might consider periodically reinforcing outer edges with a stay stitch within the seam line. Can help blocks and quilts not distort/stretch, but even with my tiny stitch, I typically go around at least the entire perimeter of the top with a stay stitch.

If the border of my quilt is made up of small pieces - piano keys, for example - it is imperative to me to stay stitch around the edge to keep the pieces from coming apart.

I do not backstitch - on occasion i will tie a knot at the end of stitching - such as when stopping .25 inch from an edge for some reason.

If the stay stitching is puckering - i try to adjust the tensions so that it is laying flat.

Of course, I had to learn all this from experience!