As a sweeping generalization no EH tube will last as long as USA/Northern European made tubes - used tubes are just that and who know's what sort of sordid life they may have lead before you got them. But if the used ones are about 1/2 the price of the EH I'd try 'em as they are generally quite long lived tubes and I've only seen a very few of them (7968/7591/6GM5) that were bad.
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