According to AIP, you need to have a forecast that is valid for at least 60 after planned ETA.
I could be wrong but I think the following reference overrides the 60 min ref.
58.2.9 Due to the continuous weather watch provided by TTF, the 30 min- ute buffers required by paragraphs 58.2.7 and 58.2.8 do not apply. Flights which will be completed within the time of validity of the TTF may be planned wholly with reference to the destination TTF.