Days Since Last Visit is a dimension, not a metric. If a hit starts a new visit, it checks the timestamp of the last hit (if there is one), and buckets the visit based on the number of days in the past the previous hit was.
Are there any specific instances where you're seeing it work incorrectly?
You're right, it is a dimension. My mistake.
Interesting that you mention it will only check on a new visit. As mentioned above, in production at the moment, we have multiple customer ids that last visited say 9 days ago, and have not visited since, yet Days Since Last Visit returns 9.
I don't see any specific instances where the dimension is not working correctly. Some customer ids we check have it recorded correctly, and others don't. I can't paste screenshots on the forum, but have sent them to client care and am waiting for a reply.
Yeah, for anything that requires looking at personal data, customer care is definitely the best way to go here. Let us know if anything develops from the customer care side of things!