The risk of guns becoming damaged in storaqe, long or short term, depends on a lot of things and environmental conditions may be the most troubling of possibilities. My friend stored some very nice rifles in cases under a bed for a season. When he next looked at them they were encrusted with rust and were never the same. Humidity, temperature, type of material they're wrapped in (foam lined cases are not a good idea) and whether they're sealed or open to the air are just a few things to consider. The only general rule I've found to be most successful is to store them in a safe or other type of enclosure with dehumidifier(s) that are regularly serviced (reset) and enough open air space around them for good air circulation. All of that within a stable temperature environment (a basement or garage where temperature variations can be significant is not a good idea).
A good wipe down of all metal surfaces with a quality penetrating oil never hurts either.