it's 200 GB per year if blocks are at max 4 MB capacity, so need not to worry, put bitcoin conf to blocksonly=1 until idb finishes
Discussion
Does this just look at the block headers and not try and verify all transactions inside each block?
No, that wouldn't be a true verification of the blockchain. It with that setting your node ignores uncomfirmed transactions being broadcast around and only pays attention to confirmed blocks.
Thanks! That's what I ended up doing. I have a big message to myself to delete that later which I will probably still forget about.