“Can dentures last a lifetime?”

No, dentures do not last a lifetime. This is due to wear and changes that will occur in the mouth and bone structure. Plus the fact that dentures can break.

They could, just don't lose them. I see patients in care homes and they regularly lose their dentures. Dentures often have to be relined. Your mouth changes and the dentures become loose. They can be relined chairside or for a more durable reline sent to the dental lab. When the dentures are sent to the lab, you are often without them for 24 hours. Dentures do break and teeth can break off. These can all usually be repaired. When you take your dentures out at night keep them in a cleaning solution. Don't let them dry out.
The recommendation is that dentures may need to be replaced every 6 years.
But that depends on the patient and how well they are doing. Insurance will probably pay for new dentures after about six years, depending on your insurance.

No they don't as we advance in age the mouth ridges change, therefore they need to be looked and checked at a 5 year period.

It's possible, depending on how much wear and tear they experience depending on the strength of your bite.

Be realistic. Do you have anything else made of plastic that you use everyday with extremes in temperature (ice cream and hot coffee) that you grind together that will last a possible 40 - 50 years? The only thing that lasts a lifetime is your heart!

While a good set of dentures are constructed from a high-impact resistant acrylic base and very strong resin teeth, they will ultimately lose their luster and pick up stain over time. In addition, eating hard items may cause chipping of the teeth. Weight gain or loss in excess of 15 pounds or so, will affect the way the dentures fit and feel. So, I guess if you are really happy with your dentures and you get 10-12 years of service from them, you should feel happy.