When Did You Install Car seats?

With twins on the way, I’m wondering when to install the bases for their infant seats. I don’t want to be caught off guard with an early labor and not having installed them, and at the same time haven’t installed them just in case we were to be in an accident before they arrive, rendering them unusable (we went with bugaboo turtle air car seats soooo I’m definitely not wanting to have to replace them at their price points lol).

We are in the final stretch and I’m getting anxious about being ready— car seats are one decision I haven’t been able to make!