Many budding writers - myself included - are often told to "start small," usually meaning to first sell short stories or poems before progressing to things like screenplays or novels. The latter is often recommended to be restricted to stand-alone novels or films, emphasizing also that said first novel or script should not be too long. (Mostly novels, as screenplays are required to stop at 128 pages.)
But I wonder if that is not always the case. David Farland once suggested to write what one wants to write, be it serial or singular, depending on the individual tales' needs. (Tom Doherty said something similar when he appeared on Writing Excuses.)
For instance, I have several stand-alones and quite a few series mapped out--some being trilogies, others consuming every number between four and seven volumes, and one whopping nine-volume cycle. (The "trilogy of trilogies," as I'm calling it for now, has a more or less definite story arc for each volume, but I won't spoil it here!)
Am I using sequel bait? I'd like to think not, although that isn't always a terrible thing, either. Many of these wrap up one story arc but either open another or are nested within a larger conflict.
My very good friend and mentor recently helped me form the skeleton of a middle-grade comedic fantasy novel (now forming sinews and muscles, in case you wondered). This project holds its own story, but I can see it becoming a trilogy or tetralogy; it's sequel-flexible, like Cornelia Funke's Inkheart or the first Pirates of the Caribbean movie. It can stand on its own, but if I feel that an extension can comfortably be added, I won't hesitate. And no, I'm not in it for the money; gods know that I don't make any from writing nowadays.
The other issue is large books. Something like The Stand or War and Peace or Les Misérables or The Count of Monte Cristo. Much like series, starting out by publishing giant novels is said to be difficult. I'm still trying to figure out how to expand my own "novels" (which are way too fast-paced) to a proper scope, but I think the same principle applies of not compromising too much at the expense of one's work. Cuts are necessary, obviously, but one must hew close enough but not too close to separate content from fluff.
The great thing about large novels, in my opinion, is that they can inspire multiple films or even a television series, like many modern YA adaptations or Game of Thrones. One of my current stories is one long novel and three screenplays to capture the entire plot (yes, I adapt my own work).
Of course, this advice may not be fit for all; this is mainly how I view it for my own literary career.
PS. - I'm trying to blog more now. Humblest of apologies for my insanely long and unintentional hiatus.