This place is one of my son's favorites! We've gone 3 or 4 times over the years, usually taking between 90-120 minutes. The 'Feast' which is many courses takes close to 2 hours. Seating usually takes 5-15 minutes.
For Epcot Forever, I'd show up 15 mins prior to ADR and then let my server know we'd like to finish by a certain time to find seating before the show. They'll be happy to work with you. We often request this now at WDW and servers seem to appreciate knowing what pace we prefer in advance.