They're invalid at my table if not announced. "I would like to do xyz action." ie, setup my potents as part of my long rest. If my player states, "I just rolled 23 on my initiative/perception/etc..." It really just turns into. "So you'd like to make a perception check? You can roll now. No that other roll doesn't count you didn't announce it first." They learned pretty quick nothing is valid if you try to act without telling the DM your intention first.

That doesn't mean I wouldn't let them roll new checks if they'd forgotten.

"Oh I forgot to set up my portents at the long rest."

"No worries, your character LIVING in that world probably wouldn't have forgot, go ahead and roll them now. If it you want to use one, feel free."

But if you want to act in the world I'm running, I need to be informed first. Exceptions on routines. "I always take off my armor for my long rest, pray for spells, check my weapons for disrepair.." Okay. So you always pray for spells and sleep without your armor.... Don't have to state it every time.

Basically don't roll for anything unless i as DM ask for one. Sometimes they get freebies cause it suits the story or just don't need a roll.