Wills don't lapse or become invalid over time. They are built for the long haul. You shouldn't have to renew it or replace it with a newer one. In the past, I've probated wills that were forty or fifty years old without any real issues.
Like a last will and testament, a power of attorney should be good for the long haul, especially if it is a durable power of attorney. It's just like the name suggests; they are durable.
Now I suppose that a POA can have a time limit contained within the body of the document. I don't think that I would ever draft one with limitation like that, unless of course it's a limited POA created for a specific transaction or period of time.
Now having said that, I don't want you to think that a will or POA should never be replaced.
As a general rule, estate planning documents are written to anticipate the types of changes that each of us encounters during our lifetimes. However, estate planning documents do need to be revised from time to time. Rarely are the changes necessary because of the passage of time. Rather, they need to be changed due to changes in circumstances.
For example, perhaps you and the daughter that you wanted to serve as personal representative have had a falling out and you want to name a different child. Or perhaps the child that you named as your attorney-in-fact in your POA moved far away and it's no longer feasible to rely on them to help you out with the day-to-day stuff. Under those circumstances, it may be better to name a different child who is also local to help you out. You don't have to name someone else, but it may be more practical if you did.
Finally, although POAs don't generally lapse due to time, sometimes the folks who receive them become a little nervous because of their age. For example, a bank may be concerned that a 10-year-old POA may have been revoked or replaced at some point. You can't really blame them. After all, they don't want to be on someone's business end for taking a document that has been revoked.
To put their mind at ease, you can attach an affidavit or certification to the document affirming it is still in full force and effect and that the person presenting the POA is the duly appointed and acting attorney-in-fact. Doesn't require a new document, but rather an affirmation made under oath that the document is still valid.