In the F70 and F100, landing gear retraction takes just 9 seconds, but extension takes 32 seconds. These are accurate figures taken from real-world documentation.

The difference in extension and retraction timings is due to the different aerodynamic effects the landing gear has on the aircraft in various phases of flight. Immediately after takeoff, the aircraft is at a high power setting, accelerating, and wants to decrease drag as quickly as possible, so the landing gear is timed to retract in the shortest possible time using the maximum hydraulic system pressure available. 

When on approach, the aircraft is in a very different situation. It is likely in a much slower, low-energy state and with the engines at a lower thrust setting. If the landing gear were to extend at the maximum possible rate, this would cause a large, sudden increase in drag. The sudden increase in drag would cause a significant change in pitch, and the autothrottle would struggle to react fast enough to maintain the target speed. This would put the aircraft in a very dangerous low-energy state. 

The solution for this was to slow down the landing gear extension by limiting the hydraulic pressure supply to the system. Instead of a sudden increase in drag, the slow extension allows for a more gradual increase in drag, meaning that any changes in pitch or thrust settings is much more manageable by the AFCAS and ATS.