Let me fill you in on something..I inspected my old rear brake shoes and they looked fine...Earlier this year, I was 1/4 mile from my house, only doing 30, applied the rear brakes and the rear wheel locked up...The lining de-laminated from the shoe and jammed the rear wheel. I did a long screeching, locked up rear wheel stop....I was lucky the road was empty, and I managed to keep the bike upright.
Replace the rear shoes...it's relatively cheap, and you won't have to worry about an unexpected lock up.
I cringe thinking about a few of the places the brakes could of locked, and might of killed me....
Don;t mess around...!!!!