Hawgnman -

From what I've learned - White oaks will produce acorns in 30-35 yrs. Trunk diameter will vary of course depending on location and competition with other trees - but generally 8" diameter (breast height) trunks would indicate 30+ yr old trees, and they should be dropping acorns.

Oak trees that have been allowed to grow in full sun (old pastures, parks, etc) will have a much larger canopy and produce more acorns, than same age trees competing in a harwoods setting. If your trees are tall, with few branches, and not much of a canopy - they will not drop as many - it stands to reason. If its your land, you can thin them and increase the canopy in 5-7 years for more production of acorns.