I understand Nebulae like the Eagle Nebula are fairly dynamic regions of space, so I find it interesting that we have photographs of the same region over a 27 years time span and at a glance, the structure of the Pillars of Creation appears virtually identical.

I understand that 27 years is minuscule on the cosmic timescale, but what order of timescale would be necessary for the evolution of Pillars of Creation to be are apparent to a casual observer? hundreds of years? thousands?