Prompted by early experimental realizations of plasma-optical components, we examine how finite formation times affect the quality and scaling behavior of a plasma grating induced by the ponderomotive potential of two counter-propagating pump laser beams. Ponderomotively driven gratings provide an alternative to ionization gratings, which offer significant advantages in terms of stability and contrast, but exhibit notable drawbacks regarding repetition rates and material modification. Here, in addition to parameters discussed in prior work we identify the pump pulse duration ${\tau }_p$ as another factor for the dynamics and persistence of ponderomotively driven plasma gratings. Based on full Vlasov simulations we predict the maximum density grating amplitude as well as its lifetime as a function of electron temperature $T_e$ and laser pulse duration ${\tau }_p$. For interpretation and modeling, we use a generalized form of a known one-frequency kinetic model to a finite-bandwidth scenario. Based on these investigations we predict the influence of ${\tau }_p$ and $T_e$ on the maximum achievable grating performance, providing a detailed explanation of the observed grating scaling. As a general result, we find that even gratings generated by laser pulses of less than a few hundred femtoseconds duration ${\tau }_p$ allow for very efficient utilization up to picoseconds, provided that the plasma temperature is not too high (e.g., $T_e\le 100$ eV).