Agree with @julies1949: there is NO RIGHT OR WRONG ANSWER here, just a whole lot of variables to take into consideration.
A Reception must be long enough to greet every guest, and thank them for coming… and to provide a bit of refreshment… that can be anywhere from a glass of punch and a slice of cake (1 hours) up to a full on many many hours all day & all night affair (6 to 12 Hours)
(Where I live in Canada, many Brides marry in the afternoon between 2 to 5, afterwhich there are Pictures, a Cocktail Hour, Sit Down Dinner, and lots of partying… not uncommon here to see a Reception Party go on into the wee hours… 1, 2 or 3 AM, so the full Reception could last up to say 8 Hours or longer. In other countries in the Commonwealth, things are similar too… with Morning Weddings being popular, and there is a Wedding Breakfast / Brunch afterwards, then a Dinner, then a Party)
In the USA, Weddings tend to happen later in the day, and Receptions with full on meals tend to go 4 maybe 5 hours on average… then if someone wants more partying, there is “an After Party”
In truth, what you choose to do will be a lot more about your “vision” and your “budget”… and how those 2 things dove-tail together.
Hope this helps (somewhat),
EDIT TO ADD – My first Wedding (Circa 1980) I was married at 4 PM. Followed by Photos and a Mix & Mingle Cocktail Hour… then a 4 Course Sit Down Meal (Dinner at 6 PM). Then the Cake Cutting & Toasts, Speaches etc. First Dances, and then Partying. Around 11 PM, my Groom & I went to change into our “Going Away Attire” got back just before Midnight in time for the Midnight Buffet. More Dancing… more mingling. And around 1 or 1:30 AM we were gone. The party was just beginning to wind down.
This time round…
Mr TTR & I Eloped to a Destination Wedding (just the 2 of us, saying our Vows on a Beach). After our Honeymoon we had a Back Home Reception… it was an Evening Party. Cocktails & Hors d’Ouevres – Champagne & Cake – DJ & Dancing. It ran 5 Hours (8 PM to 1 AM).