Generally speaking in the UK (and many other countries), any literary or artistic work remains under copyright until the end of the 70th year after the death of the author. Is this too long (or should it be extended)?
Copyright should last for this many years after the author's death:
Copyright should last for this many years after the creation of the work
Note that it's perfectly possible to answer non-zero to both questions at once: it might be desireable to make copyright last for (say) 20 years after the death of the author but with a minimum period of 50 years after the creation of the work in case the author dies before it can be exploited to its full potential.