I have some peppers that are probably 5 or 6 years old and still doing well. I'll periodically (every few months) trim some of the older branches off, and the plant just puts out a flush of new growth. Spring pruning of some old growth helps to keep the plant size manageable, and tends to stimulate the new branches which often have the most blooms.These are greenhouse grown plants, and I don't see that they are near the end of their lives yet. If I'm energetic enough, I unpot and repot with a little new mix every couple years, but with some of the larger plants, it is now too much trouble.
Renais

My long-term plants had start declining around year 4. But then, with so many plants I had stopped trying to extend them. (All in pots, btw - in-ground might well be a different story.)

Dennis

I have a 6+ year old Hungarian Wax, and this year it produced more pods than it ever had before.

In general, yes, they tend to lose vitality over time, though.

Josh

This is a 9-yr old purira that still makes plenty of fruit.

That's awesome, Willard!
Do you grow it hydro year round?

Josh

Amazing!

Yes, and I keep it pruned because of limited space.

I had a Pequin for three years before it quit on me. Large pot and simply brought indoors after pruning. I was saddened when it didn't "spring" back to life the 4th year.