Can I pay the annual patent fee for several years at a time?

If the patent office charges the same, it is ok, and the patent office calls it advance deposit. However, once the patent office adjusts the annual patent fee, the advance payment is not enough, and it is likely to expire.

I suggest that you'd better entrust a special organization to manage the annual fee.

Global Huitong Patent Annual Fee Agency Co., Ltd. is the first professional patent management company in China, and has developed its own patent online management system, providing free patent deadline reminder, patent fee inquiry and other services.

If you are interested, you can check the company name and see the details.