Using three-dimensional Go lattice models with side chains for proteins, we investigate the dependence of folding times on protein length. In agreement with previous theoretical predictions, we find that the folding time tau(F) grows as a power law with the chain length, i.e., tau(F) similar to N-lambda, where lambda approximate to 3.6 for the Go model, in which all native interactions (i.e., between all side chains and backbone atoms) are uniform. If the interactions between side chains are given by pairwise statistical potentials, which introduce heterogeneity in the contact energies, then the power law fits yield large values that typically signify a crossover to an underlying, activated process. Accordingly, the dependence of tau(F) on N is best described using tau(F) similar to e(rootN). The study also shows that the incorporation of side chains considerably slows folding by introducing energetic and topological frustration.