Older vampires more resistant to the sun

The younger vampire moved to the mouth of the crypt and stared at the
rows of headstones and crosses. It was almost dusk, but the light still hurt
his eyes and he had to shield them with a hand.

“How come you don’t mind the sun so much?” he asked Larten.

“Your eyes adjust after fifty or sixty years,” Larten told him.

Gavner grimaced. “I hate the way you make the decades sound so
casual. Fifty years is a long time.”

“Are there any exercises I can do to make my eyes stronger?” Gavner
asked.

“Try focusing on far-off objects,” Larten said. “Fix on something in
the distance and hold on it with your eyes almost shut. Slowly widen them.
When the pain goes away, take a break, then focus on something else and
repeat.”

“That will help?” Gavner asked dubiously.

“You will start to notice a difference fairly soon,” Larten said.

“How soon exactly?”

“Ten or fifteen years,” Larten said with a straight face.

***

The Saga of Larten Crepsley: Brothers to the Death, Chapter 4