How early is too early to book vendors?

Hey ladies! I just booked my venue for September 24 2022, and I’ve started reaching out to a few vendors such as DJ and caterer to get pricing estimates. I’m running into a few vendors that are already booked up entirely for 2022- which makes sense due to covid. So how early is too early for me to get the mains things, such as a DJ, caterer, and photographer? If I really like their services offered and would probably have booked them later on, is it a good idea to book them now even though it’s 18 months in advanced? Thank you!