Checking my WK stats page I realise I only have exactly 3000 more items locked items. I have already done 5,831 lessons so far, so that means I am roughly 2/3 of the way through (just by virtue of being on level 38).
I have burned 3777 items out of 8,831 total items, so about 42% already. even though I still have unburned items from as far back as level 3, and even an apprentice item from level 18 (that wasn’t recently added in the content update), I feel pretty good about this.
I have been at this for about 1 1/2 years (started 10 December 2017), and I have had some ups and downs in my leveling times, but the last third should go a little faster.