Although Bergèse, as a scenarist makes 'his' Buck Danny appear more grizzled and war-weary, as an artist, he mostly kept to Buck Danny's original look, although in the latest albums the lines on his face appear a bit deeper. Likewise his companions Tumbler and Tuckson have kept their same look throughout the series.
Bergèse, as a writer, gives Buck Danny a more worn-out and battle-hardened persona, while as an artist, he mostly keeps Buck Danny's original appearance. However, in recent albums, the lines on his face are drawn deeper.  Tumbler and Tuckson have also maintained their consistent look throughout the series.