4 year lifespan. More human than human is our motto here at Tyrel Corporation. They age. They take on all traits of people including getting old in the latest models.
Deckard is a Replicant. The unicorn seals it. He nods, understands his place and leaves. Credits. I love the Gavin Rothery theory that Deckard is a memory replicant of Gaff, which completely explains the dreams and how he knew and why Gaff is so standoffish.
If you have read Do Androids Dream of Electric Sheep nearly everything by the end of the book is artificial.
He and Hampton did work on the story for Blade Runner 2 and he was going to direct it but his schedule wouldn't let him.
When it comes to shitting on Ridley you are doing so based off his treatment of your precious franchises. The movie he made just prior to that was a huge success and nominated for best picture. He may be old but he is still better than most young directors but ageist GAF won't accept that.
There is no "sealing" it. People have their own interpretations of the film, and that's all there is to it.