BB works very well on my E61i but since installing it I have to enter an unlock code. That happens after a minute of inactivity. I can not seem to find a time interval to re-set.

I would like to remove the code entirely or put a very long interval on.

Any suggestions much appreciated ...

It can be done.

If this device is connected to a corporate BES, that's likely where the enforcement is coming from. If that's the case, you have no options on your end to change it. You will need to request an exception/exemption from the IT staff that manage that server.