The only sure way of knowing if is ready to bottle is to have stable SG readings over a period of time. Hefe yeasts are fairly aggressive and can finish fairly quickly. The time it takes for the fermentation to finish is also dependent on how the temperature of the fermenting wort was controlled. Fluctuating temperatures can change how the yeast will ferment the wort or even stall leaving fermentables.
The airlock will show activity during fermentation and after the fermentation is complete. A bubbling airlock only shows that a gas is passing through. It can be CO2 produced by an active fermentation, CO2 being released from solution after the fermentation has finished, or air caused by an atmospheric change in air pressure.
Trust your hydrometer. A little extra time in the primary will also reduce the amount of sediment that settles out in your bottles.