One risk is that the invention doesn't turn out to be commercial, which means that early filing of a patent application would be a waste of money. Another risk is that someone else will file earlier on the same invention, which means you might lose your rights ever to get a patent or even to practice your invention. Inventors are probably more likely to be able to judge the risks that their invention won't sell than the risks that their application is filed too late. The problems of relying on interference practice are many. Usually you will not be able to rely on any documentation that isn't collaborated by a non-inventor.
Interferences are very costly.
They are MUCH more expensive than the costs normally associated with getting a patent. If you don't file your application within one year of your first public use or your first offer to sell, then it doesn't really matter, because the subject matter will be unpatentable to you. All other countries use the first to file system. Recommendation Consider delaying filing an application as a business risk that you need to balance with the other risks, like the risk that the invention isn't marketable. Keep a laboratory notebook, with descriptions of all that you do.