To keep your Fox air shock in the best condition you need to regularly clean and lubricate the air sleeve. If you are good with this and do the routine as regularly as the manual suggests, your original seals will last a long time and will simply need a wipe and inspection before re-installing. However, if you let things slip you're gonna need to replace 'em more often than that if you aren't going to wear expensive hard anodised parts!!
The eyelet bushes on a Fox shock are designed to allow rotation of the shock in one plane. They are designed as the sacrificial parts in a high stress environment!! If your bushes didn't wear, something else more expensive would. Also, if you allow your bushes to get really bad before changing them, they can do damage to other parts. And you can bet your bottom dollar those parts will be more expensive than the Bush kit!