We kind of are, 20 years is an approximation I think, I'd have to go listen to the spark cast again and see if they explicitly say he's 20, but it said in the books that when he was 14 he looked like an 18 year old olympic athlete, so I think he could be 18 or 19 during this.
And even if it wouldn't change that much naturally, his voice might change due to the fact it's 20 years of pure combat. They literally freeze the guy and only unfreeze him to fight
One way or the other, Steve Downes didn't do the voice for him in this series, that won't change, an it kind of sucks.
