Most Financial Powers of Attorney are known as Durable Powers of Attorney. That means that upon signing the document (and the document is notarized), your appointed Agent will be able to act on your behalf right away, as well as after such a time as you may be unable to act for yourself. This ability to appoint someone else to step in and act for you is one of the primary reasons someone chooses to execute a Power of Attorney, so it is important to ensure the financial document you are signing does indeed include the language to make it “durable.”
A “Springing” Financial Power of Attorney, in contrast, only goes into effect when you cannot act for yourself. Until you are deemed incapacitated, your Agent may not step in on your behalf. This allows you to maintain sole control of your financial affairs until such a time as you are unable. However, if an emergency arises while you are unavailable, such as a resolving an insurance claim while you are traveling abroad, your Agent would not be able to step in for you.
Generally, as long as you are appointing someone you trust as your Agent, you should be confident to sign a Durable Power of Attorney document to cover any unexpected situation that may arise.