Thread:Howlingwolfjoey/@comment-24751497-20190824192552/@comment-24727405-20190824200141

It wasn't an speculation nor assumptions. It was stated in the volume that a "full year" passed since Priestess was rescued and joined Goblin Slayer. Here's what I found from the narration:

vol 6 ch 5 (in Cow Girl POV):

"A year--it had been a year since he went on that adventure to save that priestess girl or, more accurately, to kill goblins."

Same chapter (in Pristess POV):

"It had been a full year since the four of them had become a party."

It was stated multiple times, even in chapter 2 of vol 6, that there's a full year time gap when the story takes place. If the story takes place explicitly a year after they started the story, that means the character aged regardless of which character aged. Look at Re:Zero, even they have a full year time gap and every characters aged during the story. So regardless, if a full year has passed, then everyone aged. Plus, Dwarf Shamen joinded, HEA, and LP joined Goblin Slayer months before the main story takes place in vol 4, so they age regardless.