Hi Tim.

In BJ, the lifespan of Motorbikes of two wheels and sidecar is 13 years, and trike for 12 years.
Don't be so worry about it, after 13 years, you can still sell your sidecar without a license, although that makes it illegal, the price will not be affected so much.

As I know, there's only tiny difference on price of legal old bikes(older than 10 years) and smuglle in same conditions ones in China.