The award notice will state if it will end or reviewed so that will help. It did used to be a year but now they are over run they have set it to 6 months before reassessment and people now are having a 6 month extension to their award due to the virus causing such a backlog. Check your letter and if it is renewal then call them now otherwards you could be left with no PIP as an end award does not keep payment until assessment is done