Since time is of the essence, I tried to price 2-day 2-way shipping into the deal which is why 3-weeks is the only way it makes sense.
A company that does "baby stuff" rentals has a model where shipping is particularly expensive because car seats and high chairs are bulky. They have "free shipping" but the first week costs double what the second week costs and then each week thereafter is minimally expensive because the thing is where it is.
For example, a high chair costs $60 for one week, 90 for 2 weeks, and 110 for 3 weeks.
I wouldn't follow their model because typing on a planck for 10 days is just when it starts to feel okay. If someone has to return it after 7 days, they will invariably have a bad experience. 2 weeks might be long enough for something like green switches vs brown, but I think 3 weeks would be necessary for green vs blue.