I’ve had a rather heated discussion about this a while back. So this is my personal approach and I’m more then sure that others will not agree with it 
First of all: I do not mind, non extreme, luma noise, I do mind chroma noise.
I apply denoise at the end of my processing.
Initially this was born out of necessity due to having an old somewhat slow machine without opencl. Denoise-ing very early in the process had me waiting multiple seconds with each slight slider adjustment later on. Not workable. I now have a more powerful machine and that need has gone, but…
I notice that certain modules introduce noise and this is more obvious when denoise is not applied yet. In some cases you can reduce the noise that is created by moving the module to a later point in the pipeline, in other cases it is a sign of over-adjusting. Both are reasons for me to denoise at the end.
The downside might be (is?) that denoise (profiled) is applied early in the pixelpipe and applying it late might introduce side effects to you earlier editing. So one might need to slightly adjust some settings in other modules afterwards. Then again, going back-and-forth is part of my workflow.
Again: Just my 2c.