Hard to quantify, but I'd say I spent the better part of an entire year (full time) preparing my dissertation in developmental neurobiology. This included pulling and reading several hundred primary research reports, writing the dissertation, preparing the ~ 40 multipanel figures in the dissertation. This was before digital imaging existing and required shooting my data (e.g. Southern blots, thin layer chromatography) with a 35 mm camera, producing 1000s of prints to get that perfect shot (variable f-stops, exposure times, etc), cutting out the images, gluing them on cardstock into a multi-panel fig, re-shooting, etc...
There were at least 6 or 7 drafts leading up to the final version, which was expected to be nothing less than perfect, in terms of formatting, grammar, spelling, etc. Currently getting a numbing feeling shooting down my spine even thinking/reflecting on that horror.