Quote from bone:
Yes, they recalculate their values ( and therefore their lines ) on-the-fly as market trading ranges and price scale value areas change. If you print out a hard copy of the chart, and then look at the same study bands at a later period in time, you will see what I mean.
I personally would prefer a more "static" study with more stationary results to backtest - like pivot points. Whether it's BBs or Channels or PPs you are essentially performing a variation on a trading range study.
There are some technical studies that are a serious challenge to realistically backtest and achieve some sort of real world results in my opinion. Don't get me started about wave counts...