If you were the FBI, and you had a backdoor already built into the software running on that server, would you really confiscate it and take four days to use it

If you were the FBI, and you had a backdoor already built into the software running on that server, would you really confiscate it and take four days to use it rather than leaving it running and hoping nobody notices you came by to activate it, and/or having it be activated over the network?