  We study conserved models of crystal growth in one dimension [$\partial_t
z(x,t) =-\partial_x j(x,t)$] which are linearly unstable and develop a mound
structure whose typical size L increases in time ($L = t^n$). If the local
slope ($m =\partial_x z$) increases indefinitely, $n$ depends on the exponent
$\gamma$ characterizing the large $m$ behaviour of the surface current $j$ ($j
= 1/|m|^\gamma$): $n=1/4$ for $1< \gamma <3$ and $n=(1+\gamma)/(1+5\gamma)$ for
$\gamma>3$.
