I think I must like a relaxed fit.
Could be. Preferences sure vary.
I find the HD 600 fits me in the sense that it is actually ergonomic. It has medium clamping force (my 20 year old one anyway, new probably higher), but that makes for a secure fit with the perfect size and shape of the ear cups. Unlike many other headphones that might be comfortable but don't really fit a human head and ears like my super large Ananda or the round Beyers (Edition models with low clamping force, the high clamping force models are just plain uncomfortable).
I will admit though that my HD 600 could use new pads, the old ones are getting a bit flat.
I'm just hesitant because they cost 39€ and, especially since the redesign, will make them sound brighter. At least Sennheiser sells original pads that don't change the sound completely.
Before I bought my HD 600 I always thought it was overhyped. That opinion has changed, there is a reason it has stayed popular and nearly the same für 24 years now, to me it's a fantastic headphone.
I would still say that it is overpriced though. Why should it cost 311€ (regular price)? It should really be a 200€ headphone, especially since they moved the production from Ireland to Romania. It went on sale for 200€ recently - the next time it does I might have to get a second one