It's still not correct to say there is an obligation to defend design patents. That term implies a certain thing--that what you are obligated to defend will be diluted if you don't do so.
The patent itself will not become diluted, thus using the term "obligation to defend" is incorrect. It may be a good idea to use it to help establish trade dress protection, but your design patent will last just as long and still be enforceable even if you choose not to defend it.
The patent itself will not become diluted, thus using the term "obligation to defend" is incorrect. It may be a good idea to use it to help establish trade dress protection, but your design patent will last just as long and still be enforceable even if you choose not to defend it.