It is suggested to change oil more often than the mfg says. So was wondering on my 2002 F250 with four zerks, for just normal driving, should I grease the ball joints every 7500 miles instead of the recommended 15,000?

Also a wise friend says to just give each zerk only two pumps from the grease gun. His theory is if you pump in a lot you will disturb the seal with all the old grease coming out. Is that wise or not?