I go hundreds of miles (several months) between lubes. A spot of yellow acrylic paint marks one rail so I know where to start and when I'm finished. I use a couple of cable ties as markers so I can do one sector at a time. With these navigational aids, putting a drop on each pin takes 3 minutes and 3ml of lube (about 20 cents).
To check stretch, I wanted a number. I put tension on the chain by lashing the rear brake lever and fastening a weight to the pedal sticking out forward. With a caliper, I measured several rollers to be sure all were the same. Then I measured across 11 links and 12 rollers, as much as my 6 inch caliper could handle. I subtracted the diameter of a roller and divided by 11. Each link was .499... inches, just under half an inch. I've read that chains may come from the factory slightly under half an inch. This one hadn't worn to half an inch after 3,000 miles. (It's a single-speed bike; I'm sure not shifting helps.)
I soaked the chain out of curiosity, to see if it was as grit-free as it looked. Now when I have to remove the wheel, I can keep it simple by removing the chain.