6 days and still bubbling the airlock?

Wait another week, take a gravity, and package if appropriate

 

Different recipes, yeasts, health of the yeast, fermentation conditions (temp) can cause differences in the length of time that fermentation is active. Like GreenKrusty says, wait a week, and if the bubbling has ceased by then, take a gravity reading. If the reading is close to your expected final gravity wait 3 more days and take a second reading to confirm the first one. If they are the same (or only a point or two different) you're good to proceed to bottling/kegging.

 

Don't judge fermentation activity by the airlock. When you think it's done, check with the hydrometer.

Don't rush your fermentation. I never check until 14 days into fermentation to see if its completed. Even if you've hit your final gravity some additional time on the yeast cake is beneficial to clean up off flavors.

 

Those darn air locks cause more worry to Brewers than anything. I am with @VikeMan opaque air locks.

 

But you could still hear them 'burping' (or not 'burping')!

Cheers!