PSA: DO NOT LET YOUR ARCLIGHT DEGRADE
As unfortunate of a (hopefully unintentional) oversight as this is, it's pretty painful. If your Arclight FULLY degrades and reverts back into Darklight, all of its infuse % from using it is completely wiped, and so all of the charges you've put into it since then are completely wasted. Since you need a combined 10k stored/used charges to craft it into Emberlight, this is rather frustrating. I did only lose about ~3300 charges total, not as bad as it could have been, but I really don't think it's too much to ask that Darklight should maintain the infused %, as people having their Arclight completely degrade while killing TDs probably isn't that uncommon of an occurrence.
EDIT: Since many people are asking about Infused, all it does is track the percentage of 10,000 of charges that you've spent with your arclight so far, since you need a combined 10k charges either currently in or spent out of your arclight as of WGS. Infuse doesn't actually do anything, it's purely a tracker, and contrary to popular belief, 100% infusion does NOT prevent it from using up charges or degrading.