Should I have more than one successor? The answer is YES. But you need to prioritize the order in which the persons would serve. Let me give you an analogy...
A hypothetical scenario
Let's say you're going to give the power of attorney to a loved one or a trusted friend. What happens if Billie Bob can't serve? When you draw up that statutory power of attorney, you should also name an alternate, just a successor, just in case something comes up where Billie is unwilling or unable to serve.
You need multiple persons
This means that from the standpoint of who is going to be able to pick up the reigns, you need to think about multiple persons. Also, you always need a list of potential people who can take over and run the company.
Even if you don't plan on hiring anyone, maybe you should collect resumes from time to time to see what the talent pool is and cultivate the database. That way, if something unexpected happens, you're not caught in the lurch, scrambling backwards, trying to identify the key personnel and key employees to keep the business running.
What you should do
In like manner, if you're engaged in an old family business, you need to look at who's in the family. Who is the person best suited to take over? And if the person Is well suited, do they have the desire and interest to follow in your footsteps?
So all of these are evaluations and assessments and conversations that need to be had so that you can have a successful business succession plan. It should not be one that is wrought with what you desire but what could possibly happen because you have had the necessary conversations, you have identified key people and you see that their interests are in alignment with your vision for the company.
And then you can prioritize those successors according to their strengths, and you have a plan A, B, C or D. After all, the ultimate goal is for the company to continue to run. This is the company that you built and the one that you want to be your legacy. You want it to continue to be profitable, in your retirement, or if you should leave it.