Working for Marriott, I've come to be familiar with timelines and booking windows for a variety of programs. The size and complexity of the event typically determines the time needed to complete all necessary planning components. Here are some useful standard to follow:
• The standard window for an event with 10 to 100 peak rooms, a general session, breakouts, meals and a reception, for example, is three to six months, with few booking as far as a year in advance.
• The standard window for an event with over 100 rooms but fewer than 500 rooms and with a similar meeting structure is more like nine months to two years in advance.
• Beyond 500 peak rooms, availability is spotty. In many cases, such a large group requires multiple hotels, a convention center, all-space holds and may be considered a "citywide." Citywides are a completely different bird, so I'll stick to the basics for now.
• Let it be known that most hotels cannot easily accommodate more than 300 peak rooms with fewer than six months notice (with the exception of filling cancellation holes and off-season vacancies.)
Keep in mind I'm using the term "book" lightly here. Once the rooms and space have been contracted based on the guidelines above, no further planning needs to take place with the hotel's event team until closer to arrival. Menus, Audio Visual, Linens, and Set-Ups can be confirmed as late as 10 days before arrival (assuming no special menu items need to be ordered or items of the same sort.) In fact, the banquet teams and chefs won't have your program on their radar until 10 days prior to arrival.
This is not to say that the hotel isn't prepared for your arrival until 10 days prior. Generally speaking, they're holding off on the nitty grittiest of details until this point in time to ensure accuracy. I wish some of you could come to our meetings and see how many days in a row we have meetings reviewing every last detail of your event repeatedly for over a week!
With these standards in mind, you can create your timeline accordingly. Don't stress about what hors d'oeuvres you'll pass at your reception or how many registration tables you'll need in the foyer of your general session when the event is an entire year away. During the contracting phase, the "big picture" is all the hotel needs to see in your RFP secure ample space.