I don't have a computer so when I am doing an E2E panto I am working from the back of the machine. I go all the way to the edge, in fact I usually go off the edge a bit. I think most hand guided people do. I have a clear plastic that I keep over my panto and mark it with masking tape so I know where to stop. My mark is even with the very edge of the quilt.
The only drawback I can see happening is sometimes, if your design loops out then back in, you can fold over the very edge of the quilt with stitching and I have had that happen when I first started. I simply removed those few stitches that did that. Now when I baste my edges my basting stitch is more like 1/8" from the edge instead of 1/4. It helps stop that fold over issue. I don't think quilting all the way to the very edge detracts from the design as that is the nature of E2E designs, especially pantos (as opposed to an all over free hand E2E) as most are designed that way. I also feel that the binding will help anchor the stitches. In the case of a panto, I would much rather have the quilting disappear under the binding than come to an abrupt stop if the quilter inadvertently had the machine set to end the design too soon. Additionally, some people like to have a larger than quarter inch binding. While 1/4" is the norm how do we know if the client is going to do a larger binding? If they do then the quilting is going to disappear under it even if the Longarmer set the machine to stop 1/4" from the raw edge.