The shuttles were expected to last about 4X as many launches. Many systems have been upgraded along the way and a major overhaul on this one was pretty recent. My feeling as an engineer is that a well developed existing system is bound to be safer than a brand new one. Safer does not mean safe in terms of never having an accident. It may even be found that the overhaul introduced a problem though there is little point in speculating at this time.
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