How do Modifier-Based Features and Modifier-Setting Items Interact?

For a feature that is limited by your ability score modifier, how does usage count change if your ability score changes midday?

The specific scenario in question is Flash of Genius on our negative intelligence Artificer, who thanks to the minimum can use it once per day to apply penalty to a saving throw (the feature notably does not limit it to allies).

If they used this feature, then wore a Headband of Intellect, would they now have 3 more uses, though with +4 instead of a negative modifier? If not, how would it work? The headband uses attunement, yes, but only confers the benefit while worn on the head, so it can easily change partway through the day.