Marek Denko is a very talented artist. I love his personal projects. I think his projects takes considerable time since he makes every thing himself. The truth is quality work takes time to ensure the best is achieved. If I remember from watching some interviews of some of the world top archviz studios, projects take up to 6 months and it is nice to know some clients have come to understand the need for time to get the best quality of a project. If u also check out work by Jesus Selvera (Zuliban) (very talented artist), his projects take time as well. This may also be due to working on it on and off. Quality work should not be rushed.
I agree with Alex Roman's approach as well. I remember a discussion I had not too long ago with a friend. He mentioned how some areas of cg will be handled differently in the next 3 to 5 years. Modeling everything by hand is going to be a thing of the past. We already have photogrammetry which is being adopted very fast in the industry for games, films and archviz. This is a faster approach for both modeling and texturing rather than doing everthing by hand. In the possible future, there are talks of AI handling modeling assets. I remember how certain 3d artists used to feel about using character creation softwares like DAZ or Poser being unoriginal work but currently, scanning is being used for characters these days for games. It's all about speed and quality. I have always watched the industry closely and I remember during my masters degree course, noticing how game engines would change the archviz industry. My fellow coursemates thought otherwise. So I always advice that observation is key, and trying to get with where the industry is moving towards. The fact is ''clients don't really care about the process, it's the end result that matters'' feng zhu used to say this. He is an awesome concept artist. I think sometimes, we get too purist about things when practicality should be the norm.
For a lot of us, freelancers, time is money as a lot of clients want work done in a week or two. So here is where the balance need to be worked out. So I have realized, putting every detail in takes time (I would very much love to add them if I have the time) but a satisfied client is also important. So if u are very fast and the quality of your work doesn't suffer or get compromised, even better.