This would also include hot cocoa and such that is served to guests. To me it does seem short since the couple (I'm helping a close friend plan her Christmas themed wedding) is planning to serve cocoa, hot cider, espresso to the guests during the cocktail hour and also have it available after dinner with cake/dessert.

Should it just be limited to dessert and then serve cider seperately with the cocktail hour since it's not part of the espresso menu? Or ask for service for the entire evening?
They are having the ceremony and reception at the same venue.

I would say too long. I would reserve the espresso bar for dessert only.

Hot Cider, Hot Cocoa and even espresso might be too heavy for cocktail hour. People are just getting into the reception site, they will probably be hungry. I would let them have real food first, then the espresso bar.

Hot cocoa may be too sweet for a pre-dinner snack. People will probably skip it and go for soda, water or a bar drink.

In college, I worked at a Country Club. I worked lots of wedding and black tie parties. There was always a espresso bar with dessert. However, it was more espresso, lattes, cappuccinos. But, hot cider and hot cocoa were expectable too.

Anyway, this would also happen at dessert, which would take place the last hour of the reception.

2 hours?? Definitely not.

Actually, I wouldn't even serve these types of drinks until after dinner if I am also having a cocktail hour before dinner. People typically prefer these beverages after dinner if there is a menu involved.

I would save it for after dinner. Most people won't take advantage of it during the cocktail hour, anyway.