Agree with most of what you say.
... but you ARE required to have a forecast, that covers your ETA plus 60 mins (TTF or TAF). If your ETA falls within this, then you don't need to obtain an update.
AIP
73.2.11 Flights which cannot use TTF will plan the flight on the current TAF until such time as the destination ETA falls within the validity period of a TTF.
Jepp
6.1.2 The issue of a new forecast by a meteorological office, such as a routine aerodrome forecast, shall be understood to cancel automatically any forecast of the same type previously issued for the same place and for the same period of validity or part thereof.