I'd say the hardest part is writing a comprehensive patent. Defending it and amending the claims later down the road is easy if you have the base material to a

I'd say the hardest part is writing a comprehensive patent. Defending it and amending the claims later down the road is easy if you have the base material to amend the claims with (i.e., material you wrote in your original patent). Also, paying a top firm to write the patent is generally 50-70% of the cost of getting a patent allowed. Litigation is a different matter entirely...