I only read the first page on this thread but I started with a fixed deck 36" bunton many years ago. It was a total PIA to adjust blades. I tried to schedule the ones that wanted something other than the standard height together so I only had to adjust the blades up and down, 1x. Gas was a lot cheaper back then and I had more time so I didn't mind driving a little bit more to do this.
Then I got busy and stopped the madness! Eventually I moved on to only 60' ztrs with quickly adjustable decks. My profitability increased and it was easier so my overall satisfaction with my work improved, as well.
My advice, gut it out while you have time and are making a name for yourself. When you are busy and don't have time, cut the PIA customers from your client list.