On Feb 22, 2017, at 5:17 PM, John Allen wrote:

Is the any recommendation as to the TTL for TLSA records?

An hour or less. Depending on how time-sensitive your email is. Keep in mind the refresh time of secondary servers, setting the TTL much below that does not help much.

I would imagine fairly short as if the is a problem you want the old ones gone ASAP!

Yes, that's the basic motivation to keep it reasonably short. -- Viktor.