upkeep of a collection list would be doable with strict follow up whenever something new is purchased, but the hours required to start something like that?
I don't even know how many transformers I have, at least hundreds, probably well over a thousand. If I managed to keep cataloguing to just 5 minutes per figure that's over 5000 minutes, that's 167 hours. assuming I spent an hour a day creating a list that's 23 weeks doing an hour a day, nearly half a year.
as if I could be bothered,
and then there are all the insurance company requirements mentioned aby others above,
it's probably better picking the 10 or 20 most expensive to replace (or most special to you) figures and worrying about those.