dust in iMac 27" (Retina, late 2015)

The fans on my iMac have started coming on more frequently over the past 6 months plus they seem louder. Plus i've got little dustballs constantly falling from the exhuast port in the back central. Despite cleaning my studio frequently, my flat seems quite dusty, nothing I can do about that. What I'd love to do is open the back and give it (especially fans) a good clean. However I read advice from 2009 post that this was not not advised at the time. Is this still the case with a 2015 iMac?

Over the years, I've poked around inside my previous MacBooks and Mac Pros so I generally know how to behave doing such an operation.

regards, David