For example spending a P2SH (2of3 multi-sign) would take a much bigger space than spending a P2WPKH.
If you want a guess here are two ways:
(1) https://blockchair.com/bitcoin/blocks#f=id,input_count
Blocks usually have transactions with a sum of 5k-6k inputs so lets just take the lower value 5k. Remember that normal blocks with normal transaction have a much lower number of inputs that 500 you said.
1609190 UTXOs would take 321 blocks. Each day we should get 144 new blocks that means it would take between 2.2, so lets just say 3 days to clear it out.
(2) If we assume all of the inputs are P2WPKH (since a lot of the addresses in the link in OP are of this type) and with 500 inputs and 1 output the weight of this tx is about 136000 and each block max weight is 4000000 that means the block can contain 29 of these transactions or 29*500=14500 UTXO. The total of 1609190 would take 110 blocks which is less than a day to clear out with 144 blocks per day.
Thanks for this!
Looking at the numbers with a bit of median then we can expect anything from half a year to a nearly a full year of blockspace needed to spend or consolidate that assuming all are economically viable to do so or those are normally spendable or not this new type of ordinals or runes or whatever!
I do wonder why f2poll owns most of those dusty address but that's probably something only they know if they do at all!