If you're interested in knowing the limits of Microsoft Forms, you can check out this kb: https://support.microsoft.com/en-us/office/form-question-response-and-character-limits-in-microsoft-....
Yes, you can use the form indefinitely as long as you don't exceed the response limits by deleting the old responses. However, keep in mind that deleting old responses may affect any data analysis or reporting you do with the form.
