Another garage door sensor that may cause problems is the limit switch that tells the opener the door is closed: These are often located up at the drive motor. As the door spring weakens after years of service, this may need an adjustment. Since many models differ in how this is set up, consult your owners' manual for specifics on your model.
It has been quite some time since I had to open a garage door manually. My dad, like most people, has an opener on his garage now. After all, he is well into his 70s and all of his boys have long since moved out. He also has a remote for his TV, which gets a lot more than three channels. He would have to agree with me when I say, "Progress is good."