Jesse: You can't keep us from seeing each other.
Chief Warren Kincaid: I'm the chief of police, sport. I can do whatever I want. Like for example if I were to run a blood test on you tonight and the results made you look like Christian Slater on New Year's Eve, do you think anyone would question me?
Stoner: Rude fuckin' doll.
Tiffany: Well, hello, dolly.
Tiffany: Oh, Chucky look at us. We belong dead. Good bye darling, I'll see you in hell.
Jade: Bite me.
Damien: Come on, let me in or I'm likely to catch my death out here.
Tiffany: Promises, promises.
Tiffany: A woman spends all day over a hot stove slaving away for her man. The least he can do is the dishes.
Chucky: Figures you'd hitch us a ride with a fugitive.
Bride doll: I promise to honor, love, and cherish, till death us do part.
Chucky: You got that right.
Tiffany: Hold still honey or I'm going to poke you in the eye again.
Answer: There's two possible explanations. First, and the most likely, is that this is simply what's referred to as a "retcon." (Short for "Retroactive Continuity") A term to describe new information/rules/backstory/etc. that are introduced in order to alter the path of a story, or impose new ideas into a narrative. In this case, the series creator and writer Don Mancini needed a reason for the characters to go on a road-trip, hence he created this new idea for an amulet that Chucky need to obtain. And basically, Mancini himself has admitted that he will often change the rules for the series as needed from film to film based on the story he wants to tell, which makes this the more plausible explanation. The second possible explanation is that you could argue that the amulet will allow Chucky to transfer his soul regardless of how long he's been in the doll's body, surpassing the time limit imposed in previous films. But in all seriousness, the former is the more likely explanation. They just needed a new story-element to justify the road-trip aspect of the story.
TedStixon
Both answers work for me. Thank you.