I would think the longer perches would help prevent axle wrap up more, and may even help the springs last a bit longer because it spreads the axle footprint out on to more of the spring. After they were torqued to spec, I think I would add a weld tack to all 4 corners of each perch, just so they couldn't spread any. Gene
I think that also would be the most common thinking. Mine is however different, I believe it might actually shorten the fatigue life ( which is almost infinite) on a spring with a longer perch, in that it concentrates all the remaining movement in an effectively shorter length of the leaf, and increases angle of bending at each end of the perch, granted by not much. I don't see it as plus longevity wise other then making a stiffer spring by shortening its length, which might be useful in itself.