One of the mistakes while making Eternal Pain was working in secrecy for the most part and only making it public closer to release. As others have stated, you should do what you can to tell people about it as soon as possible like tweeting, blogging etc
I know, because I was the same. As a indie developer in my spare time outside of a full time job, there were fears that someone else could copy the idea and release it earlier than me. However, that could also be one of the reasons why you should blog about it early, so there’s proof that you came up with this idea on your own in the off chance you get accused for copying someone else’s game.
I don’t have time…
You barely have much time to work on the game, shouldn’t you be making the most of it and spend it working on the game instead? Sure, but you should think of this as part of game dev, since it’s just as important as making the game. Another option is to get someone else to do the PR so you can concentrate on the game.
Advertising for your game is important
Obviously. So, if it takes you 3 years to make the game, wouldn’t it be great to get 2 or so years of ‘free advertising’ on the side? You never know who might stumble upon your blog, maybe it’s a writer for a game magazine, just even if it’s a random person who likes what they see and then sees it on the App store a couple years later and checks it out because they thought it looked familiar – it’s worth it.
It shows you are ‘alive’ and working hard
If you don’t tell anyone that you’re indie developer, then you won’t be included in any opportunities from the community,promos or events. If you do tell them who you are but don’t update people on what you’re doing for ages, people will think you’re slacking off. I think most people can appreciate hard working people so a simple tweet like ‘still working on game XYZ’ would be useful especially to those who are fans already.
I’d like to think you’d have ‘something’ to show before making the game public rather than tweeting as soon as you get a game idea. It might take some time to develop the idea, do some prototyping or testing to flesh it out and maybe some concept art that you feel fits with the idea before eg. making a website about the game. Though, if you’re confident, I’d say go ahead :)
So basically…it’s important. It can’t hurt, it can only help.