The strong enhancement of NMR signals achieved by hyperpolarization, decays, at best, with a time constant of a few minutes. Here we show that a combination of long-lived singlet states, molecular design, magnetic field cycling, and specific radiofrequency pulse sequences, allows repeated observation of the same batch of polarized nuclei over a period of 30 minutes and more. We report a recycling protocol in which the enhanced nuclear polarization achieved by dissolution-DNP is observed with full intensity and then returned to singlet order. E.g. MRI experiments may be run on a portion of the available spin polarization while the remaining is preserved and made available for a later use. An analogy is drawn with a "spin bank" or "resealable container" in which highly polarized spin order may be deposited and retrieved.