There is no one-size-fits-all answer to how many domain names an individual or organization should own. The number of domain names that you should own will depend on your specific needs and goals.
In general, it may be beneficial to own multiple domain names if you have a large and diverse online presence, or if you want to protect your brand by registering variations of your domain name. For example, you may want to own multiple domain names to redirect traffic to your main website, or to use for different projects or services that you offer.
On the other hand, if you have a small online presence or only need one website, you may not need to own multiple domain names. In this case, it may be more cost-effective to focus on promoting and maintaining a single domain name.
Ultimately, the number of domain names that you should own will depend on your specific needs and goals. It may be helpful to carefully consider your online presence and the nature of your business or organization when deciding how many domain names to own.