Data loading for backtesting

[linuxrules]

This may be a dumb question but I noticed that each backtest loads the same historic data from the data feed ever time (resulting in a an error from IB soon enough) when I backtest the same future with the same timeframe.

It was my understanding - or belief - that NT would load data into the DB once and for all. Historic data will never change, right? So why load it again? I thought I could load 2 months, and then later load 2 more and so on, until I can finally test the whole range of say 6 months.

Also, I hoped that a second connection to OpenTick could overcome the limitations of IB. But NT doesn't seem to use that connection as a backup. Is this normal, or am I doing something wrong?

Thanks for any help or experience from others.