Did they give you a guideline like Ramiro Berrelleza suggests to his candidates? As Bridget Sarah points out, it is really unfair to assume you have unlimited time.
I would timebox it to one evening after the interview, unless I got some specific guidance.
Perfect is the enemy of done :) You'll get diminishing returns if you spend too long on it.
I started this process with Github a few years ago, stressed out about it and finally turned it in. They never got back to me... So ya, if I could take those hours back, I would ;)