Would it be fair to surmise that, in general, the awarding institutions prefer to wait a bit to ensure the work holds up over time?

Very fair, and the purpose in waiting. After all, that young pup Albert Einstein may have seemed to have a great idea in 1905, but it would have been embarrassing to give him a Nobel in 1906 and have his theory shot down a few years later.

However, the rule of not awarding posthumous prizes means some very deserving work and people will go unrecognized.

I have no problem with waiting, but they should give awards posthumously when deserved.

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Never attribute to malice what can be adequately explained by ignorance or stupidity.
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