60% humidity? Man I wish the humidity was low like that.
Fun times is playing in 95% humidity outdoors (and no......it wasn't raining.... seriously, the weather thing said 95% humidity.) Your fingers just slide all over.......
+1 to the "it's not the humidity level but the level of humidity changes"..... higher humidity doesn't seem to bother my basses or anyone elses I know of.
However.....it's safer in the case than on a stand. Stand just cries out "knock me over".

But that's a different topic!