I thought… “If I keep changing my product, I cannot afford to patent each and every change in the product”
The truth is, it is not necessary to patent every change or modification made in your product unless such change is a non-obvious or a significant change. Generally, a well-drafted patent description would anticipate such changes and still include them in the patent description as alternate embodiments. Minor change in size, materials used in the manufacture is the core of a mechanical invention or change in the concentration of ingredients or operating temperature is the core of chemical invention can be anticipated and provided for in the patent application and there is no need to file additional patent application for such changes/modifications. Each case must be analysed in its own right as each invention by definition is unique.
Remarks: This is not legal advice; it is mere information for knowledge on the patent system.