I noticed the party often have problems with visibility and sight in dark places. I was reading through the players handbook to see if there was anything better than the light spell for my mage as we have the same problem sometimes in our games. I found lanterns are amazing, a hooded lantern gives you 30 foot bright light, 30 foot dim and last for 6 hours, also you can put it down and it won't go out. You also get Bulleye lanterns which give light in a 60 foot cone of bright light and 120 foot of dim light. they also last for 6 hours per pint of oil which is cheap as heck.
It seems like a cheap investment that could save the party allot of trouble.
ps love the show