Hey Simon,
this was because many people wanted to use many bars. Like 500 000 and more. There are traders who want to test EAs for the last 10 years. Personally, I think it is not necessary, but I showed a method of how they can collect it.
On the higher time frames, I would use more….for example what is in the MetaTrader-Demo server in EA Studio is good:
M1: 300,000 bars
M5: 200,000 bars
M15: 100,000 – 120,000 bars
M30: 50,000 – 60,000 bars
H1: 25,000 – 30,000 bars
Cheers,