Some seeds sprout as soon as they fall from their mother plant. Other seeds might stay dormant and and sprout only on the following year. Still other seeds may keep dormant for many years till they 'decide' to sprout. Such seeds form seed banks inside the soil.
Business Seed Banks
Similarly, in the business world some ideas start sprouting as soon as they come to mind. The person who gets the idea can start right away working on it. Other business ideas may stay dormant in the mind for many years till the right time for them to 'sprout' comes. It is totally OK and natural that you keep some ideas brewing in your mind for some period of time that might reach even years before deciding to let it out and actually act upon it. Make sure, however, that you do not keep all your ideas heavily guarded in a seed bank forever without allowing any of them to see the light!