Time doesn't stand still while you're developing your product!

When making a development plan for your product/service, it's easy to think that for everyone else, time stands still.  I see a present need for a product.  It will take me 3 years to fully develop the product and be ready to sell it.  Gosh, what will life be like in 3 years?  Will there still be a need for my product?  Will it be solved another way by then?  Or will the problem simply go away, lose favor, no longer be in vogue?  Will a competitor have solved the problem by then?  If only we knew.  So, try to keep your development cycle short by perhaps coming up with a simpler version of the product, or outsourcing some of the work, etc.  Being paranoid will save you here...being ignorant or dismissive might kill your company.