Usually Century rides clearly state that "This is a ride, not a race" which is not to say that there are some who ride it as fast as they can- but there are plenty of others who are just out to have a fun relaxed ride. Centurys frequently have shorter distance rides included, from 12-12 miles on up to about 70-something as well as the 100 miles (which is usually ore like 102, or 104!!)
Anything that says Time Trial or Criterion is not what you want!!
Nanci