applying for multiple entry visa

I visited China for the first time in July on a single entry visa and again I will be going in January on a single entry. I asked about a double entry and was told by reception, no not unless i am Chinese or for business reasons. I would like to apply for a double entry or multiple entry so I can see my girlfriend more often. We plan to marry next year. How can I be accepted for a double entry or multiple entry? It doesn't matter if it is 6 or 12 months.
How long must you wait from visiting China once before you can apply again to visit?
How can i have 60 days rather 30 days?
If anyone manages to help me..........thank you in advance.
Mark