They get left in place. Not sure how long the stucco will stick to it was the main concern, but setting them was like setting a feather pillow. My guys eyes would brighten right up when the 17'4" was on the job. Some days those precast ones are extra heavy, esp. when your down to 8 guys that day.Seen the sheet metal bent lintel, Trade named after the inventor builder? can't recall it... save a couple of pounds money and weight every window in steel.
I'm suprised the LEED/Eco manure hasn't encouraged their use to cut heat flow over openings.
In Florida there is a galvanised 16 gauge scored surface 8" square pre made lintel single use form, the tin is the tensile element for up to ~8' openings then you start adding rebars in the form cavity. Less planning than precast,no hoists needed and salt tested,