Even though proxies for rent are available in quite a few proxy rental providers, the answer to the question is not as straightforward as you might think.
First you will need to consider what would you be using it for and what
is the expected outcome.
Let’s say that you are concerned about privacy:
Then your target is to keep your real IP and physical location private, most likely you will need a proxy server every time you use internet.
If you are looking to protect only sensitive activities you could activate the proxy only when needed, but doing so might defeat the purpose if your browser fingerprint, cookies and cache are not cleared every time the proxy is turned on and off.
Suppose you need a static IP to access a particular webservice that whitelists access by IP.
In this case you would need to rent a static IP4 proxy server or IPv6 proxy server for as long as you need that IP or the service whitelisting it. You might also be surprised to find out that in most cases renting a static IP proxy server is cheaper than getting a static IP from your ISP.
In another situation you need to check how your ads appear to search engine user in different locations to calibrate your SEM efforts.
In this scenario you would need the proxy for the time that your project is active. A static IP would not be required in this case but it might help to get consistent results as rotating proxies will add the IP as a variable in your tests
These are only a few use cases. Static IP proxies can be used for gaming, data scraping, Whitehat website security checks, access to geo-restricted information while abroad, search engine optimization and even social media posting or even link building automation.
All public webservices are available via an IPv4 address so on most occasions that is what you will be using.But, IPv6 is becoming increasingly available so you might want to consider it for use cases where IPv4 IPs are getting blocked or flagged.
There is also a choice to be made between Socks5 proxy server and Https proxy server rental.
The bottom line is that once you have made a decision on protocol and IP layer that you need to use, renting an IPv4 proxy server or an IPv6 proxy for as long as you need it and then simply cancelling it when it is no longer required is the way to go.