On-chip Physical Unclonable Functions (PUFs) are emerging as a powerful security primitive that can potentially solve several security problems. A PUF needs to be robust against reversible as well as irreversible temporal changes in circuits. While the effect of the reversible temporal changes on PUFs is well studied, it is equally important to analyze the effect of the irreversible temporal changes i.e. aging on PUFs. In this paper, the authors perform an accelerated aging testing on an FPGA-based Ring Oscillator PUF (RO-PUF) and analyze how it affects the functionality of the PUF.