RBC shelf life is around 100 - 120 days. You've been changing them over at this rate since you were in the womb and will continue to do so until the day you die.
Shit, man, women bleed for a week every month and don't croak from it (except for when their husbands finally snap from all the nagging).
So, no... there is no need to worry about "wearing out" anything. Just give blood at whatever rate keeps your CBC panel in check and makes you most comfortable.