Arapahoe, a general rule of thumb is 2-3x's the average bar for that particular pair for long bars. I'm assuming that your referring to 15 min bars as i mentioned above? (there obviously were no long bars on the 4hr chart where this trade is based on) Looking at approx. the last 650 15min bars (this can be done by exporting chart data in dealbook360, then opening in excel, for example), the average high-low is 20 pips (open-close is 9 pips) so 40-60 pips (18-36 high-low) would be cause for concern. I agree that it seemed a bit questionable based on the last few bars prior to entry as they were somewhat borderline (biggest high-low was 37 pips prior to entry, and biggest open-close was 30). There were no gaps present (which would have tipped the scales in favor of invalidation), and the low of 1.7476 came in almost exactly at the 127.2% extension of the prior (overnight) 15min upswing (from 1.7503-1.7598) which in turn resulted in a bullish 15min ABCD pattern that also added a bit of confirmation to the buy. In other words, there were more reasons to take the buy then the iffy single long bar warning sign (the more obvious these warning signs are, the better).