I wonder what adjective do you normally use to describe an action / a task which as time passes causes you to wear out and makes you exhausted. These kinds of jobs are not at all boring at first, but by the lapse of time make you tired and maybe fed up with continuing them. These actions/jobs/tasks etc. are somewhat eroding your patience body after by the passage of time. So, after a period of time you might not be interested to them (at all).
— Even if you have a team, lexicography is a/an.................job. It requires lots of patience and love. Otherwise, it can make you exhausted after a short while.
I don't know any word in English encompassing this concept, but I think using "erossive/eroding" in a figurative sense (of course if it works,) would be my needed adjective.