  Recent studies relating the approximations for the equations of state for
thin shells and their consequent perturbative evolution are extended to
thin-shell wormholes in theories beyond general relativity and more than four
spacetime dimensions. The assumption of equations of state of the same form for
static and slowly evolving shells appears as a strong restriction excluding the
possibility of oscillatory evolutions. Then the new results considerably differ
from previous ones obtained within the usual linearized approach.
