Here's a question. Is it actually common practice to test your code by leaving it to run for weeks while inputting random stuff and observing if it leaks memory

Here's a question. Is it actually common practice to test your code by leaving it to run for weeks while inputting random stuff and observing if it leaks memory, sets bad values or crashes? If not, why not? That'd catch any "mad user bugs" and all kinds of accumulated collateral damages from the sea of complexities which might be overlooked if routines are only tested individually.