When to install car seat base?

So we have two car seat bases, one for each car. I’m 31 weeks 3 days. I know not to put the car seat in too early because of the possibility of an accident and then no longer being able to use that but I do want to install the bases so when we head to the hospital we can just grab the car seat and go. I’m not sure how much of a risk it would be to install the base only too early if there’s an accident, but want to get your opinions on when to do it!