We present results on the percolation loci for chemical clusters and physical clusters of long lifespan. Chemical clusters are defined as sets of particles connected through particle-particle bonds that last for a given time $τ$. Physical clusters are sets of particles that remain close together at every instant for a given period of time $τ$. By using molecular dynamics simulations of a Lennard-Jones system we obtain the percolation loci at different values of $τ$ as the lines in the temperature-density plane at which the system presents a spanning cluster in 50% of the configurations. We find that the percolation loci for chemical clusters shifts rapidly toward high densities as $τ$ is increased. For moderate values of tau this line converges to the low-density branch of the liquid-solid coexistence curve. This implies that no stable chemical clusters can be found in the fluid phase. In contrast, the percolation loci for physical clusters tend to a limiting line, as $τ$ tends to infinity, which is far from the liquid-solid transition line.