Okay, I'm not sure if this was explained in the original series of Doctor Who, 'cause I've seen hardly any of it (except for some of the Tom Baker series with the cool scarf), but there's something I don't get about Time Lord regeneration.

Do Time Lords age? Well, obviously they AGE, but do they age physically? Like, if nothing or nobody kills them, will their bodies eventually die of old age before they regenerate, or will they just keep on living until something other than old age causes their death - like vampires in Buffy, or the elves in LoTR? I'm a bit confused.