Unless the Durable Power of Attorney document that you sign is “springing” it becomes effective IMMEDIATELY upon signing, NOT when you become incapacitated. The Durable Power of Attorney ceases upon death, so it cannot be used to avoid probate.
Additionally, a Durable Power of Attorney requires more updating than any other estate planning document discussed here. The laws with respect to powers of attorney change frequently. I recommend having your attorney update this document at least every five years, to ensure compliance with the law.