I thought 10% leakdown was really good? Is this 10% purely from the valves, or total - ie you did a wet leak down.
Unless there was some other compelling reason to take the head off, I wouldn't personally.
FWIW - the instructions always say to do a leak down with the engine warm, but no one ever does.
I install many used engines, No choice than to do it cold....A good engine will return low leak-down rates.