RH is RH, (and that's a seperate thread alltogether) but studies have shown that the RH and not the total humidity is what really matters, so the 55 i'm sure won't hurt anything (they might age a tad slower, but who keeps 'em long enough to age anyhow?) I'd let them warm up to room temp before lighting, but that's probably just me, and probably doesn't effect anyhitng.