Generating new addresses for each transaction doesn't increase your risks of a collision.  The risk is not simply the risk of a collision alone, but also the maximum potential losses that such a collision could represent.  A single collision with one of your many addresses only exposes the coins associated with that particular address, not the total amount of bitcoins that said wallet.dat can access.  Reuse of addresses may limit your raw risks of a collision, but reuse also increases your maximum potential losses since more bitcoins are concentrated under fewer addresses over time.  Either way, the risks are so small as to be astronomically unlikely.  If a collision were to ever occur, even intentionally, it would be big news if someone could prove that it had occurred.