Are there any deadlines for completing a qualification at Unisa?

Yes, there are time limits for completing qualifications at Unisa. The time frames are as follows:

3 years to complete a 120-credit qualification (e.g., Higher Certificate, Advanced Certificate, or Honours and Postgraduate Diploma).
6 years to complete a 240-credit qualification (e.g., 2-year Advanced Certificate or Diploma).
8 years to complete a 360-credit qualification (e.g., 3-year degree or diploma).
10 years to complete a 480-credit qualification (e.g., 4-year degree).