The ideal debounce time typically falls between 200-500ms, with 300ms being a common sweet spot for many applications. This range balances responsiveness with efficiency.You can view some more information on human reaction times here. Reaction times are key to understanding this recommendation:

The average human reaction time is approximately 200-250ms Most people need about 300ms to recognize that their input has had an effect User typing speeds vary, but the average person types with intervals of 100-300ms between keystrokes

Your example using 250ms is actually quite reasonable and aligns with these findings. This value:

Is long enough to catch multiple keystrokes in a typing sequence Is short enough that users don't perceive a significant delay in the system's response Corresponds well with average human reaction times

For search filters or auto-complete features, you might adjust based on these considerations:

More complex/expensive operations: lean toward 400-500ms Simple operations where immediate feedback is critical: lean toward 200-300ms Mobile interfaces: consider slightly longer delays (300-500ms) to account for different typing patterns

Rather than a fixed rule, the best approach is considering both human factors and technical constraints for your specific use case. Your instinct to adjust until it "feels right" is valid, but starting with 250-300ms is generally a good baseline.