You're both right or both wrong.... there's no "one size fit's all" to describe Architecture, but there is is (pretty much) to describe human nature, it's people that drive these things and people will try to take advantage of you to further their own ends (getting their work done in record time, perhaps), not whether it's architecture or town planning or landscape design or product visualisation or....
So my advise is more to set out as you mean to continue, if you're prepared to work long hours and weekends at the outset, then don't think that's going to miraculously change later on unless you can somehow re-invent your business and your clients, those clients are going to expect you to continue to work long hours and weekends as your business develops. Why wouldn't they? This is the business model they've bought into and you can understand why they'd expect this to continue.
If you feel you must put in the extra time because your fresh in the field and trying to develop customers then perhaps try to divide your work time into 9-5 weekdays strictly for the client and the extra time in developing you and your skills and your libraries etc, so the client sees the benefit indirectly and doesn't develop unreasonable expectations that will continue through your working relationship.
Obviously there are different strands of Architecture, the area I'm in is much more time pressured side of the business than perhaps some of the top end clients of Juraj & Veronika who - from what I can see - are also in a much more powerful position in the client / Visualiser relationship. So most of us are going to encounter different problems with our client relationships than they are. For example I'd guess they are less concerned that their clients might walk away if J & V want to have the weekend off than many of us here would be