I'm trying to find out more about how far back it's possible to request event logs from nodes. I've seen reference to blockhashes only being available from contracts for the last 256 blocks, but I can't find information on what nodes may elect to return from filters or older block requests.
As a practical example, let's say I logged certain activity from a contract 6 months ago and want to prove today that this activity was logged (as a basic notary service). A naive filter could request the information from a node, but how many nodes would send you back a possibly large amount of data from 6 months ago, or even 6 years ago?
If you run your own full (archive) node, is it a configurable option? If you don't, is it possible to locate a node which offers a full archive? Do people think this will become a pay for service in itself?
This could be come more relevant when state tree pruning is factored in: https://blog.ethereum.org/2015/06/26/state-tree-pruning/