Here are some:
"The phone rang, I dropped the glass, and the cat howled, and still the child continued to cry despite my lullaby, leaving me, as the babysitter, to wonder what I could possibly do to put an end to this rapidly deteriorating situation."
"The lawyer, having convinced his client to plead guilty, was now faced with the problem of avoiding the revelation of his own part in the criminal act, a lapse in judgment that, while done with the best of intentions, was nonetheless a violation of his oath as an attorney, a violation that might conceivably result in his disbarment, indictment, and even imprisonment."
Example sentence - We walked quietly in the long hallway.
Example sentence - If I am careful with my books they will last a long time.
Example sentence - Her hair was long and silky to touch.
Example sentence - He was slipping in and out of sleep during the long drive.
Example sentence - She had a long trudge on her way to the gallows.
Example sentence - She had long admired his kindred spirit.
She studied long into the night to prepare for her exam.
Example sentence - The cabin had been left in disrepair for a very long time.
for example "how long is a metre?"
All a sentence has to have to make it a sentence is a subject and a verb. For example, "She ran." would be a complete sentence. 'She' is the subject and 'ran' is the verb. But a sentence can be as long as the writer wants it to be. The longest sentence I've personally ever seen was about 3/4 of a page long. There's no limit to how long a sentence can be, really, as long as it's a well-written sentence.
Example sentence(s) - The salt is coarse ground. She has long, coarse hair.
Example sentence - He had no idea how long it would be before the crime was discovered.