Interesting topic. I'll take the liberty of jumping in with two observations, the second of which may bring some interesting responses. One - if you, personally want to enter a contest, the time to do it is now. Two - in my own, personal opinion, the time to enter a contest is - never.
I've been building models for 49 years, and I've taken part in quite a few contests - local IPMS ones (dating back to the late sixties, when the IPMS was a new organization), regional events, and international ones. I've also served as a judge quite a few times - including the 1990 International Scale Ship Model Competition at the Mariners' Museum, where I used to work. On the basis of that experience I'm convinced that model contests do at least as much harm as they do good.
In the first place, winning an award in a contest, by definition, merely establishes that
in the opinion of the judges your model was superior
to whatever other models happened to show up. The above post from Mr. Smith is a good indication of how the personal opinions of judges, frequently influenced by some odd sort of "group think," can influence the outcome. In my own favorite field, ship modeling, there's an influential European organization that goes even farther than Mr. Smith's examples: it bans weathering. In my opinion that sort of behavior doesn't encourage better modeling; it stifles individuality and creativity. At my age I have better things to do than build a model according to somebody else's standards, just for the sake of winning a ribbon or a trophy. I don't need somebody to tell me whether my model is better than somebody else's; I'm perfectly capable of figuring that out for myself. And if I think Model A is better than Model B, and somebody else thinks the opposite is the case - well, does that really make any difference?
Secondly, model contests have a way of bringing out the worst in people. Some of the most ludicrous exhibitions of infantile, bratty behavior I've ever seen have been put on by alleged adults who didn't like the outcomes of model contests. (On more than one occasion I've been guilty of saying some stupid, regretable things myself at contests. That's another reason I don't enter them any more.) I've known people to drop out of model clubs because of contest results, and though I've never actually seen a pair of modelers lay into each other with their fists, I've heard that it's happened. One of the losers in that 1990 Mariners' Museum competition spent several months afterward bombarding the organizers with sour-grapes letters, eventually threatening to report the judges to the authorities. (His balloon got popped when he discovered that there are no such authorities.)
Some years ago Mystic Seaport Maritime Museum staged a "juried exhibition" that I liked. The modelers brought their models to the museum, and the judges identified all the ones that came up to a certain (pretty high) standard. All those models were put on public exhibition at the museum for several months. None of them was labeled "best" or "second best"; all of them were simply identified as excellent models. In my opinion that's as competitive as modeling needs to be.
I greatly enjoy looking at, talking about, and learning from other people's models, but there are ways to do that without holding contests. I'm a big believer in non-competitive exhibitions. The club I currently belong to, the Carolina Maritime Modelers' Society (meetings at the North Carolina Maritime Museum in Beaufort the last Saturday of every month at 2:00; new members and visitors always welcome) holds such an event every May, in conjunction with the museum's annual Wooden Boat Show. The club members bring in their models (the subjects of which range from RC sailboats to clipper ships to Japanese battleships) and display them in the museum auditorium. Before the show starts we set the models up in front of a plain background under photographic lights and I take pictures of them; I make the set of photos into CDs and pass them out at the next meeting. On the day of the Wooden Boat Show thousands of visitors look at the models and talk to the modelers. We operate a booth in which kids are invited, for $2.00 apiece, to build models of fishing trawlers from pre-shaped wood parts made in the museum's boat shop. (Most enthusiastic customers: Girl Scout troops. Average construction time: 15 minutes. Typical reaction to the experience: ecstasy.) Everybody has a great time, everybody learns something, and nobody argues with anybody about anything. I've been in that club for about ten years, during which I've never heard an uncivil word spoken by anybody. Maybe that's at least partly because we don't have contests.
All the above is, of course, highly personal opinion. I know lots of folks get a great deal of enjoyment out of model competitions, and that's entirely their business and their choice. But give me a non-competitive exhibition any day of the week.