[DNSSEC-Transparency] Validity wrt TTL

Hi, In a long response on the getdnsapi-users list [0] I reasoned about validity and time. I'm sure this list could have good input on this. [0] https://getdnsapi.net/pipermail/users/2016-February/000164.html A short version is - should a log limit submissions to those who are "fresh"? - if so, what are resonable values for freshness? - would this be useful for more than spam mitigation, i.e. good for attribution as well? Thanks, Linus