Last year I went to the Parrot festival in Texas. One of the lectures was on cockatiel breeding behavior.
Teils will "date' for up to six months before they actually mate.
It sounds like the potential couple is checking out the honeymoon suite to see if it is suitable. The male will usually do the inspection first. I put carefresh bedding in the nest box. They will go in and chuck it out which means they are setting up house keeping duties.
Make sure they have plenty of calcium, fresh veggies and pellets/seeds.
Just be patient
