Not really my specialty, but the answer is just logic. There is not a simple answer. It depends on how deep the sediments/organic material are, and what the heat flow is, and how much time there has been. If too hot, too deep, and too much time, then would be overmature. For the same heat flow, if the organic material of interest is shallow enough, will not be too hot.

In brief and general, what affects the maturity of sedimentary organic matter is mainly the haeating history (particularly the maximum temperatures with a more limited effect of heating duration). The heat flow has no direct effect on maturation. It affect on the temerature distribution in the section (geothermal gradient) in accordance to the thermal conductivity of the rocks. Different tectonic systems have variable heat flows. Rift basins are often (not allways) associated with an elevated heat flow due to its formation by stretching and lithospheric thinning. In such a case the geothermal gradient might be relatively high (if the rocks are not having high thermal conductivity) and that can affect the rate of maturity increase with depth.