I have a basil plant that is 2 years old. It goes to seed, then it looks dead, then it comes back to life. It keeps doing that over and over. We have no cold weather in Arizona that will kill the plant. About a month ago it went to seed for about the 3rd time. All the leaves fell off and now it is growing nice green leaves again. This is the same plant not a new plant from fallen seeds. Very interesting.
I never saw this happen in Tennessee cold weather always killed my plant.
You are very lucky. I have a Thai basil that is a couple of years old and that is unusual too. Most of basil used to last about 10 months before they got too woody. Now, with basil downy mildew, the only ones that survive and look good are the African ( it acts like a perennial and is very long lived), lemon, cinnamon, lime, and some, not all, of the Thai basil are partially resistant to downy mildew. They will show the disease on some leaves but survive. I got two sweet basil to mature this year without downy mildew. Unfortunately, Walmart was selling sweet basil that was infected with downy mildew in the beginning of May less than a mile away, and my last set of Thai basil had to be discarded because they got infected.