My visa expires in February 28. Should l leave before that date, or could I leave on Feb 28?

Steve, you can leave on Feb. 28.
Actually, you mean the validity of your entry permit, right? If so, can I know how long the stay duration for each entry of your entry permit is? If the stay duration hasn’t been over, even though your entry permit expires, you can still stay in PRC until the stay duration runs out.