We used recently high resolution Neutron Spin Echo (NSE) spectroscopy to investigate the critical dynamics at the antiferromagnetic transition and in the SDW phase down to the cycloidal transition of the prototype multiferroics TbMnO3 and MnWO4. We found slow fluctuations persisting deep in the collinear magnetic phase of the two studied multiferroics. Naturally one may associate them with precursors of the lower transition, but we may not exclude that these fluctuations stem from the strong frustration present in both systems. We propose to perform an additional NSE experiment on MnWO4 in order to measure the temperature dependence and the q-dependence of the slow fluctuations so far documented in the high-temperature collinear phase.