"Dear David, I am now using the ten year charts rather than the five year ones in order to get a wider perspective of the historical situation of each share that I am following. What is you view on the choice of the longer perspective?"
David Fuller's view Thanks for an important question of general interest.
Perspective is crucial and I agree that it will probably be helped more by 10-year weekly charts, provided that the actual graph is big enough so that you can see the individual candlesticks, if that is what you are using. (See also the Bigger Charts item below.)
Chart reading is a visual art, so it is essential that you feel comfortable with the graphic presentations. Inevitably, there is an important tradeoff between the number of shares that you have time to review, and the amount of detail that you may wish to view in making your assessment.
What I find from an investment perspective is that it is better to review weekly charts, so that you can ideally see at least the last important low and also the last significant high. That way you will have a good understanding of where the share is in terms of at least its last two medium-term trends.
If the overall chart action looks confusing - as in often indeterminate - it probably has not shown sustained periods of supply/demand imbalance, which is what produces significant trends. Powerful trends have an aesthetic visual appeal, of order, consistency and often rhythm, at least until they start to top out or bottom out.
Choppy, whipsaw ranging patterns reveal that supply and demand is more often than not quite similar, resulting in a standoff rather than a persistent trend. I would leave them alone until they break out and begin to trend.
When potentially interested in an instrument, you will probably want to look at more than one chart. I would not start with daily charts unless you already have a very clear mental picture of the medium to longer-term price history. Even then, you will most likely wish to update that perspective periodically.