[chalst]

Only experts can make this judgement in the short term. As time goes by, the reception of the work accumulates and it becomes increasingly possible for non-experts to judge.

It took over 20 years after the Standard Model reached broad acceptance (ie., the experts thought the theory was probably right) for the first supercollider powerful enough to observe the Higgs boson to be financed. This was enough time for policy makers to reach high confidence that the experts had not gone badly wrong and for there to be reasonably well-informed public opinion on the merits of the search.