Stevef raises an interesting point.....I'd venture to suggest these items are probably not mandated for "once-use" change....it stretches the realms of credulity to suggest that an o-ring should be changed EVERY time a dipstick is checked.
perhaps the most sensible judgement is Blackhand's......he's trained to understand the engineering judgement and does so....
I agree that O-rings are relatively cheap (though exhorbitantly -priced once they're "certified" as Aircraft components) however, like fuel in the bowser, airspace above you , etc. they're no damned good in a stores miles away on a public Holiday , with AOG and a perfectly serviceable component ready-fitted and ready for re-installation.
sometimes blind obedience can be set aside and skill,experience and common-sense allowed to prevail. Theory and practise are not necessarily the same thing....as I said before.....it doesn't cost the seat-polishing academics a bean to cover their backside, so they don't "allow" a skilled engineer's judgement -call. (bet they'd change their tune if stuck somewhere inhospitable without all the throwaway items on tap)