The time it takes a child to build a Technic set can range anywhere from just a couple of hours to days. There are several factors that influence how long the building process will be; whether the child is an experienced Technic builder or not, their age, the number of pieces, and how much the parents assist in the assembly. You can generally expect even a somewhat experienced child to take at least an hour or two to build a model, as this seems to be a common report in Amazon reviews. For younger or first-time Technic builders, the process can sometimes take four hours or more.