For whatever reason, I generally feel warmed up on my bike at 9 or so miles, or roughly 35 minutes (I'm 41). I'm not aiming to run for longer than 3-5 miles at a time, so I'm not sure I've ever going to feel "warmed up," during runs, but that does provide a good reminder that I should ideally walk for a longer period of time than I currently am to warm up.