Feeding a website a diet of backlinks from poor websites is like eating a bunch of junk food. Junk food may make you feel less hungry but it does not help your body in the long term and eating alot of junk food will likely damage your health in the long term. Stop chasing junk links and start going after strong links that will make your site more healthy.
If you are chasing after links from these low quality sites using duplicate content, then I assume your anchor text will also be the same across all sites. Besides spending too much time chasing after sites that have little if any positive link benefit, having too much of one anchor text is another issue to deal with. Good luck.