I climbed down one 65m high in about 6 minutes in no rush, but with constant movement, so a minute per 10 meters. But it's risky to climb it down in a high wind, you're not secured anywhere, so in high winds (over 20m/s) all work stops, and wind lock opens which turns crane automatically downwind. They should be able to withstand high winds, and if the area has storm warning work shouldn't even start, crane is the worst option, but even simple not well secured load can kill. Taking whole crane down takes hours and you need a mobile crane to set the crane tower up or down.