the secret of coolant mixed water is not allowing water to be contaminated with rust.
and in case of leaking hose or waterpump, it wud be easily recognisable.
for toyota LLC its not recommended 50:50 mixture as the liquid is quite corrosive to rust and metal. it may cause water pump leak. for corolla size cars, a bottle will do. for camry about 2 bottles or slightly less.
one advantage using toyota LLC is that it will change its colour from red to dark brown and later black as a sign of replacement. magic isnt it? :D
normally it will last about 40,000km.
never use coolant with anti-freezing description. only meant for cold weather countries with winter season.