The short answer is that nobody knows how often you will be called for a PIP medical assessment. Renewal claims are sometimes decided by the DWP, without being referred to health professionals. However, some claimants will have to attend another medical assessment.
PIP awards are for fixed periods. Many are short-term, lasting two years or less. People with conditions that are unlikely to get better or worse get awards of between 5-10 years. In August 2023, a new ‘light touch’ review process was introduced for claimants on the highest levels of PIP with awards of 10 years or more or who are over state pension age. These people may not be reassessed if it appears to the DWP that little has changed.
Ultimately, how long your award is made for and how often you are reassessed will depend on your individual circumstances.