Supposing you have an orchard, or planning one. And you want to add to your nursery from seed from your orchards trees. Wouldn't it be great to cut down on the time it takes to get your first fruit from the seedlings you grow. If in your orchard you plant some trees that are known to be precocious then their offspring will also be precocious. Look at the image below as evidence of what I say. That image is from a study a 100 years or so ago called A study of the results of Crossing Varieties of Apples
by Clarence C. Vincent for UMass.
It becomes obvious looking at that image that you can produce fruit faster growing apples from seed than from seedlings that you have to pay for. This is probably exaggerated because the apples shown in the image are examples where both parents are precocious. The important point to get from the study is that precociousness is an inheritable trait.
So what apples are precocious, here's a list:
Cox's Orange Pippin
Grimes Golden, same apple as Golden Delicious??
Yellow Delicious (Everfresh)
So my suggestion is that you plant a precocious apple thru out your orchard. But how do you know which seeds will have the trait. Well I'd guess that if you harvested seed from the precocious tree that they will have that attribute. And I'd also say that if your precocious tree was also a delicious apple you'd get some very good,early bearing apples. Let's say you have a Cox's Orange Pippin in your nursery. Some say this is the best tasting apple there is, and it's an early bearer. If you plant seed from apples from that tree I'd guess you're going to get better apples from a cross between a cider apple and that crab apple next door.