On our small backyard batch evaporator I always boil it out when the smell starts to change. Some of my best testing syrup from the season came from those boils. We had one boil where my brother described the smell as smelling like a clambake, lol. That syrup had a slight off taste but I would still reach for it before the light stuff.
24x24 post and beam Sugarhouse (built by Lyle Merrifield and crew)
2x6 raised flue cdl traditional evaporator
600 gallon milk tank
300 taps on combination of 3/16 and buckets