No,
Which validity period are you referring to ? There are 2 periods that I'm aware of. One is the period which I assume you are referring to i.e. the period within which, having authorized a domain with your account key, you are able to a cert without re-authorizing. This period is currently 60 days. The other period is the time between asking for a token, during which you can authorize with that token.
I'd suggest checking the divergences from the ACME draft-04 - https://github.com/letsencrypt/boulder/blob/master/docs/acme-divergences.md
I'd suggest subscribing to the API announcements category API Announcements - Let's Encrypt Community Support