It is definitely time to start thinking about it.
With any great piece of art, literature, architecture, movie and so on, they take time to create – software development is no exception. At least, it shouldn’t be.
It should be planned, considered, designed, redesigned, tweaked, tested, and re-tested, and then once the initial MVP (minimum viable product) has been launched, it should be planned, considered, tested etc all over again.
Why? Because like designing a building, it has to look aesthetically pleasing, be functional, stable and secure, stand the test of time (as much as anything can, especially in the software world) and be affordable. Otherwise what is the point? It will fail and you would’ve spent loads of money on nothing.
But to do this, it does take time, and therefore time needs to be factored in to any successful development project from the beginning. You should also always bear in mind that if your software concept has never been created before, or put together in quite the same way, then you will need to allow for longer than original given estimates.
If you are therefore thinking of creating a new application next year, for sale / release by the end of next year, then I would highly recommend starting the initial planning phase right now!
In my experience, spending more time planning always leads to a better and more successful outcome, that will ultimately cost you less to develop and maintain in the long run. I myself have often spent 3-4 months in the planning phase (including prototyping), before spending 6-12 months in development (depending on the type of project of course).
So get planning, and if you need any help or advice, then do give us a shout!