I don't think high humidity will hurt them necessarily, they just don't need it except when they shed. Many snakes are like that. 60% would be fine. You'll read all kinds of different things. It depends on the keeper. There isn't a universal agreement on these kinds of things. Some people say no humidity, some will tell you 80% all the time. My opinion is to try and get as close to their natural setting as possible. Since humidity isn't always high or low in most areas, then varying humidities should be safe for the snake. It's the same with temps. Some people say the temps should remain constant 24 hours a day, others say it should cool about 10 degrees at night. Since most areas in the wild would cool off between 10-15 degrees at night (or more) I tend to follow the "cool night" pattern. It sounds silly, but if you are curious about what temps/humidities you should keep your snakes at, I'd check the weather channel or an almanac to see what the average readings are for their native areas. Don't get me wrong, you don't want a 'frost warning' in your cages and you don't want it too warm during the day. The best thing about enclosures is that you can prevent all the 'dangerous' weather and just work with the most ideal situations.
Wow, did that make any sense at all??? lol
Anyways, my point is, moderate humidity all the time is fine, increase when they shed. It can be moist in the cage but it shouldn't be wet all the time. Okay, that's it, I'm shutting up now