that's exactly what I think. SN can handle high temperatures.
the most important thing you have to do, in regards to SN storage, is to not break the seal unless you're going to use it in the same day. because breaking the seal makes the air come in contact with SN, which brings some water to SN, then it starts slowly oxidizing into sodium nitrate (NaNO3), which can render a SN sample unsuitable for end-of-life purposes.
PPH, in the SN chapter, talks about storage.
in fact, storage is one of SN's big qualities, because it's easy to store and it can have an indefinite half life if properly stored (in its original sealed container).
TL;DR: it's fine, just don't open it unless you're gonna use it.
"Storage & Disposal of Sodium Nitrite
Sodium nitrite is stable, and can be stored at room temperature. However, it should be stored in a sealed container. Sodium nitrite is also hygroscopic. This means that when exposed to air, it absorbs water and will slowly oxidize to sodium nitrate, silently degrading over time. Oxidation will render a sample of sodium nitrite ineffective as an end of life agent. Evidence of deterioration can be difficult to determine by visual inspection.
There are no specific concerns with the disposal of any unused nitrite, and the shelf life of properly stored salt is almost infinite."