You've begged the question. If there is a line then where is it? How do you know three year drug patents were wrong and thirty year patents are right? Remember the thirty year term was bough by the Pharmaceuticals industry with campaign contributions. So what's the formula? How long is long enough? Why can't you say?
Patents are 20 years. You should bring yourself up to speed.
http://www.fda.gov/Drugs/DevelopmentApprovalProcess/ucm079031.htm#How many years is a patent granted for?