It definitely doesn't mean what you think it does
Even if you can get a corporation to admit they used the word "lifetime" on a cable/internet contract, they'll quickly refer you to the small print definition.
"Lifetime contract" generally means the lifetime of the contract - which can be any length of time they want it to be.
Guarantee that even if they did use the word on a written contract, there will be small print definition that explains that as soon as the company decides to cancel or change the contract, it's "lifetime" is over.
The tech world is always using this word and it always means the lifetime of the product, not the lifetime of the person buying it. The usual time frame for "lifetime" warranties is 2-5 years.
Other industries do the same thing. Your "lifetime" warranty on a mattress is usually about 10 years, but can be 20. Your lifetime warranty on a vacuum cleaner is normally 5. Hard disks 3. I've yet to hear of a product whose warranty ends when you die.