Extended gamma processes have been seen to be a flexible extension of standard gamma processes in the recent reliability literature, for cumulative deterioration modeling purpose. The probabilistic properties of the standard gamma process have been well explored since the 1970's, whereas those of its extension remain largely unexplored. In particular, stochastic comparisons between degradation levels modeled by standard gamma processes and aging properties for the corresponding level-crossing times are nowadays well understood. The aim of this paper is to explore similar properties for extended gamma processes and see which ones can be widen to this new context. As a by-product, new stochastic comparisons for convolutions of gamma random variables are also obtained.