How long is seder?

A complete seder can last an entire evening. The "service" part of it includes prayers and readings including recounting the Exodus and incorporates foods associated with the texts including wine, matzah, sweet and bitter herbs, salt water, a roasted lamb bone, egg, and a mixture of nuts, apples and wine (there are variations) called "charoses" (ch is gutteral, not like chair). This can easily last an hour or more because after certain texts are read they may also be sung or chanted by everyone, such as the "4 questions". Once the primary service is over, there is a complete meal served. That can last another hour. THEN there are additional prayers including a grace after meals, and much singing together with the hunt for the "afikomen" ("dessert") or hidden matza.

Then again there are folks who keep it short....and at synagogues where young people are invited it can be abbreviated. Also, since many also have a second seder (on the 2nd evening), that can be shorter than the first as well. These can be an hour to two, maybe three.