Are there studies that back up your claim? Or is this propaganda from the entrenched powers?
There are studies that show patents slow down & harm innovation.
http://www.fee.org/the_freeman/detail/do-patents-encourage-o...
Indeed, patents are good for the lawyers & entrenched players. That doesn't sound innovative to me.
To pick one area I'm somewhat familiar with, a lot of the patents in digital-audio synthesis were initially reasonable, in my opinion. Furthermore, the system largely "worked" as it was supposed to to incentivize innovation and ensure that commercializers of technology paid some royalties to those developing it. A research group like Stanford's CCRMA would develop a new synthesis method, patent it, and license the patent to a commercializer such as Yamaha, who put it in their synthesizers and paid a royalty. Without patents, there would be a strong incentive to do this monetization via keeping things secret instead, rather than openly publishing them somewhere that Yamaha could just read.
The part where it starts seeming unreasonable is when a 15-year-old synthesis method, which is by that time ancient and textbook-standard material, is still patented.
After the time period the patent / copy rights should be released to the public domain so that everyone may benefit from cheap economy of scale production.
The only reason I could think you feel this way is that it is all you've known. In most cases a couple of years worth of profits from monopoly should suffice. In reality it depends on how much was spent on the initial innovation.
One tricky issue is also the lead time to market. In the synthesis example, Yamaha came out with a synth within ~2 years of licensing the patent. But in some areas (like medicine) it can be common for it to take 5-10 years for a product to come out, in which case a 5-year patent would be worthless, because it would expire before you can sell anything.
In reality it depends on how much was spent on the initial innovation [and how long it takes to reap the return on that investment].
It seems to me that you want it to be less for your convenience, and no other factor.
The problem arises when the patents last much longer than the "innovation cycle" in an industry. As software takes over the world, we're seeing cycle times go down in many fields, but patent laws aren't keeping up with technological reality.