I have 3 ESP Eclipses that were made between 2009 and 2014. Although they all have the same woods and construction (but there is a noticeable variation in neck thickness with the oldest being the thinnest, followed by the most recent in the middle and the middle one being thickest) there certainly appears to be a correlation between the age and their acoustic resonance, with the oldest being most resonant and the newest least resonant. I wondered what this could be down to. Could it be the fibres in the wood loosening up, the polyurethane varnish loosening up, an effect of "they don't make 'em like they used to" (ie constant search for ways of cutting costs) or just pure coincidence? What are your observations and what do you think?