New Products - what is the age cutoff?
The setting Admin > Configuration > Maximum Values > New Product Listing - Limited to … determines what “New Product” means:
Limit the New Product Listing to 0= All Products 1= Current Month 7= 7 Days 14= 14 Days 30= 30 Days 60= 60 Days 90= 90 Days 120= 120 Days
Reducing this value means a more efficient query for generating a list of new products.
ALTERNATIVE: If, however, you wish to hand-pick which items show up, then turn OFF the New Products box, and use Featured Products instead. See Admin > Catalog > Featured Products to pick the products.