Is the maximum duration of tourist visa really only 30 days?

I would want to travel around China for around 3-6 months. However, from what I see in this post and most other information, tourist visa's usually grant travel for only 30 days. Is there any other way to make this possible? And how likely is the local bureau to extend a tourist visa while in China? I want to stay around Chongqing.

I am a Dutch citizen and therefore can stay visa free for 14 days, so with a visa run I could get a double-entry visa (valid 6 months). That way, I could enter the country visa-free (2 weeks), visa-run through HongKong/Taipei, use my first entry (4 weeks), visa-run again, use my second entry (4 weeks), but that still would only leave me with about 3 months total.

Do you have any general advice?