Wasn't sure about how recent a development looped strings were, but I can restring my bow in about 3-5 seconds with string and bow in hand and its a 55 lb recurve. YMMV
Actually, with a looped string, the part left on the bottom limb probably fell off, and a brush of your hand would remove the portion left on the top limb.
By and large these things come down to common sense. If you are in the dungeon your bow is strung. Marching along the road in the rain, it better be unstrung and under wraps. In the middle of the spectrum ask your GM how strict he is being.
How long should it take to restring a bow? A few rounds. A crossbow? About 20 min with help and sometimes special equipment. (It is not a quick process to restring a 300# pull metal bow on an arbalast.)
But there is a point past which pursuing realism is counterproductive. For example the English longbow vs Middleastern recuve (composite) bow debates that used to dominate message boards. While there are some definite mechanical advantages to the recurves (and 3e reflects these) the fact of the matter is that neither would work in the others domain. A Yew longbow would lose it's tensile strength in middle eastern heat and a composite bow would delaminate in english humidity. Of what use is this detail in a game? None. No archer wants to hear that the glue on his +3 strength bow just dissolved in the swamp of itchy death.