I don't think God is a sadist, but He is just. He says we'll suffer according to our sins, which is further evidence for why there is no eternal torment,
for if everyone burned forever, everyone would essentially be getting the same punishment, and what's more, why should Cain who only killed Abel burn 6,000 years LONGER than Hitler who killed millions?
I'd like to think Satan, who will suffer long after the rest of the wicked have "burned up" and "passed away" out of existence, will still be there a good while before he too passes out of existence. "
"Therefore, will I bring a fire from the midst of thee, it shall devour thee...I will bring thee to ashes...AND NEVER SHALT THOU BE ANYMORE". Ezekiel 28
The devil is not going to exist anymore.