After receiving my visa , how long do I have to travel to China?

I travel to Asia every few months, but I never know when I will travel. I would like to visit China while en route to/from other Asian countries.

I would like to apply now for a visa now and and then use it when I am en route to/from other Asian countries I visit. After receiving my China visa, how long do I have to make us of it?

Thank you.