We observe that the increase of the graphene channel length has the positive effect of enhancing the ION/IOFF ratio. Moreover, it widens the OFF region of the transistor (i.e., the range of gate voltages for which the current flowing through the device is low). This can be explained by the fact that, for a given concentration of boron atoms, longer channels contain a larger number of dopants. The combined scattering action of the dopants on the charge carriers flowing through the device gives rise to the observed positive effect. At the same time, we observe an overall decrease of the current profile. However, this detrimental effect could be compensated by operating several transistors in parallel.