> As a rule of thumb, you should only use [personal audio] devices at levels up to 60% of maximum volume for a total of 60 minutes a day. The louder the volume, the shorter your duration should be. At maximum volume, you should listen for only about five minutes a day.

Perfect, I'm just going to plug my headphones into a 50-watt amp. Then I can have them as loud as I want without even getting anywhere close to 60%, so my ears will be totally safe!