In Oz a TTF metar is valid for 3 hours and you can use it in place of a TAF.
ACMS,
In AU, not only can you use a TTF in place of a TAF, you must, the TTF supersedes the TAF for the duration of the TTF.
An ATIS that includes a METAR + trend is a valid TTF, and is generally valid for two hours -- the ICAO standard.
A TTF will be based on far more recent data than a TAF -- almost real time.
Check your Jepp. WW Text or equivalent document.
Tootle pip!!