How early would you release a trailer?

As the title say. 1 month before release? 2 months? 3? Or 10 years before launch like Square Enix?

10 years definitely, let it really sink in. Speaking seriously though I think some trailers are released too early, particularly announcement/teaser trailers in the game industry. It can have a negative, it leaves people wanting to hear the latest news and then be disappointed when they hear nothing especially at the big game conferences and events. Long enough and it can cause a game to not be able to live up to the wait or people grow tired of waiting and just move on.

You don't want to release a trailer too late though; they are a form of advertising/self-promotion, they are meant to catch consumers attention, be talked about, shared and the followed up with scattered updates to keep the consumers interest and advertise further.

I think you want to start releasing a trailer when your game has taken direction , you know where its going, what you want it to be, that you will finish it and that it isn't going to change drastically in development (like being moved to another engine/development tool).

Personally I am waiting until the week of or the week before launch, but that is just me.

I would say that it would depend upon the nature of where you are publishing your trailers & your relationship with your potential customers.

For example, if you have social media dedicated solely to content under your "developer's" hat, as it were, like youtube, facebook, & twitter; then I would say never more than a year out from release, & only if you intend to release other trailers between that trailers respective drop date, & the games release. That way the idea of your IP is kept fresh in their mind, without reminding them of countless other "vaporware" projects that both indie & triple a talk about all the time, but never produce.

On the other hand if your social media usage is more akin to that of echo607 or SRDude, where along with information about the games you are creating, you release content involving tutorials, plugins demos, game reviews, & the like; you can be more flexible. Especially if you integrate your game projects into alternate media not directly tied to promoting your game.

For example, when I write my Steam Guides, I use my own projects to demonstrate what I am talking about.

There is also the matter of how often you are posting content about your project. For example developer update videos for your patrons, if you have a patreon account; or live streams where you show what you have been creating.

Simply put, there isn't a right or wrong answer, but rather it is VERY situationally dependent upon what you have been creating.

I think a trailer is only something you do when you finished the game (or a stable demo version), because making one at any earlier point risks using outdated assets or mechanics that aren't representative of your released game, and it can take a lot of time to make a new trailer just to update important details you want to have featured in it.

Depends on what kind of trailer you're making.. if its a gameplay trailer, I'd wait until Im sure that no gameplay elements will change anymore

Generally I would stay the hell away from teasers unless you've had a huge success. Nintendo can drop a teaser for Metroid Prime 4 and have the world go crazy cause they're Nintendo and it's Metroid. A teaser from Indie Developer #10000 with no established fanbase isn't going to have the same impact. People are already invested in Metroid and care about a new game but the harsh truth is that indie and hobbyist devs generally don't have that type of fanatical devotion. I'd say a good time to release an announcement trailer is with the public demo, so that people can see what the game is like without having to download the demo, and then hopefully your trailer convinces them to download the demo. Then do a separate trailer for release, focusing more on narrative and making it a bit more cinematic and professional than the earlier beta trailer. This is all just my opinion of course, but it's a lot less to ask someone to watch a minute long video to find out if they'll like your game rather than making them download a demo only to find out it isn't what they're looking for after all. Basically, if you ask someone to watch a trailer fir a demo that's not asking them to do much but asking them to spend hours downloading and playing a demo is, but they might be happier to do so with a trailer that already lets them know what they're in for.

Personally I think as soon as you are SURE you are going to finish your game, getting a trailer and some info up is a good idea, as long as you are able to update it every once in a while. As some other people said though, releasing a trailer too late/early is a bad idea.

I would say once you are certain no major changes will be made to the core of your game and you have at least some story content and gameplay to show off a teaser trailer no sooner then 1 year before release if you intend to drop 2-3 more trailers between then and release.
Otherwise I would say somewhere between 4 to 3 months before final release.

I like the idea of using 2 trailers rather than just one. (Or multiple if you have the time)

Take this model for example: Have one that focuses on story elements with shots of the game and a gameplay trailer.

When releasing them, go for the gameplay trailer first since people want tangible proof you have a game. Maybe a month before release, then drop some spicy character /game tidbits each week on your social media accounts as a sort of countdown.

Finally on the week before the date, drop the story trailer.