Definitely
xantholophus. Age is hard to estimate as it's based on many factors. He looks close to one year old, but it's the length that is confusing. If his snout to vent length is 4 inches, he's either younger than a year old or is stunted. He looks mature but is on the smaller side, so I assume he still has some growing to do. So if that's the case, he's probably a little under a year--maybe
6-8 months-ish?? 4 inches snout to vent is still super small. If
@Kaizen ever shows his face on here, his guess would probably be the best.
That quip is both well-deserved and about as diplomatic as a ghost like me should expect: props, and sorry for being so absent. I shall endeavour to be more, um, around!
Regardless, his age/growth rate only affects his feeding schedule. If he's still growing, you can feed him every day as much as he wants. He looks healthy for his size, and you don't want him to look puffy. Take a mental note (or keep the picture you posted) of what he looks like now. You want him to look proportionally the same as he looks now. If you feed him as much as he wants and you see that his arms, casque, and back are starting to get poofier/fatter compared to the picture, you want to ease off the food to every other day @ 3-5 food items. If he is growing, you want him to be proportionally bigger than he is right now. You don't want him to become obese, so keep the picture you posted to use as a comparison.
Edit--this is only an estimate. I'm not super confident about this guy's age.