Jack breathed out as Ianto lowered himself onto him, willing himself not to thrust all the way in right then and there, because if he was going to tire him out he was going to want to make things intense, but slow. Which he was fine with. He moved his other hand up to rest on Ianto's hip, gently pressing him down as he went. "I think, regardless of whether you're up to it or not, tiring you out completely sounds to be a great idea." He stilled his hand, circling his thumb around the head of Ianto's erection instead, urging Ianto on.