Why does the store even have a lighted sign if they're not open at night

At my first thought, I would say that is an interesting question. Then I realized that the whole movie took place throughout the summer months in which the days are longer. In winter it starts getting dark quite early, like around 4:30 pm especially in a Northeastern state such as Pennsylvania. Closing time would normally be no sooner than 6 or 7pm.

I grew up in Pittsburgh, which is about 100 miles south of Erie. I agree with the previous poster about how early it gets dark in the winter. There could be another reason for the lighted sign though. Back in the 60's (and beyond) there was one night a week when all of the "downtown" stores were open late. So although they generally closed by five, on Thursdays they stayed open later. This may have also been the case in Erie which, although smaller than Pittsburgh, is still a sizable city. So the appliance store would need the lighted sign for those dark winter evenings and for that one night a week when they were open late, which would also explain why the sign was lit in the summer, when this movie takes place.

They're open probably till about 7 or 8. In the winter it would be dark at that time. Patterson's may not be open all night, but it is open at dusk/early nighttime.

-Di