All work is value-based. Never forget that.
No clients care if you spent 80 hours a week not solving their problem, so why would they care if you spent 20 solving it?
This has not been my experience at all. It's a different subject entirely, but it is very common for clients to be much happier to pay for 20 days at $550 a day than 5 days at $2,200 a day, even if they got it two weeks earlier. People are not rational.
It's complicated and pardon me if I have glossed over the details somewhat.
If you're smart, you get all of the work done in advance, then stage it over the course the next few days, providing a steady trickle to create the perception of steady progress and to have something to mention at the standup meetings. I suspect a good percentage of experienced developers with good customer management skills do something akin to this.
I really like this because it incentivizes productivity over hours in seat. IE, right now this comment is being added to my "non productive" time and I am making no progress on getting my workday done. (I have 15m left at the moment)
I am generally pretty focused, but sometimes that wanes and I find this keeps me on task. On the best of days I start around 7am and call it quits by noon, but occasionally that stretches into 2pm.
I do occasionally hop on a bit in the evening and we are all basically all on call but our stack is pretty stable so that doesn't come up often.
Has been absolutely awesome, I don't think I could ever go back. I am far happier, spend far more time outdoors and I honestly do not think my productivity has dropped much at all. I think it is far too easy to just use wall clock as a measure of working and fool ourselves that we are doing more than 4 hours of real work in an 8 hour day.
Throwaway because I'm not sure my clients are ready to hear this.