Trimming the beard

Assalam o laikum!Mufti sahib, please forgive me for disturbing you with my questions time and time again,over matters which might be trivial for you but important for me.I had asked you regarding trimming the beard shorter than a fist,and you said it is Gunah e Kabeera(major sin). In your translation of Mufti Saeed Ahmed Palanpuri’s works,you stated that it is Makrooh e Tahrimi to trim the beard shorter than a fist,and the one who persists in doing this commits a major sin. Now my question is:
There are some sins like drinking alcohol,adultery,murder,robbery etc which if a person even commits only once,they are very major sins(Gunah e Kabeera).And there are some sins which are minor but become major sins if done continously.So is trimming the beard shorter than a fist(NOT SHAVING IT COMPLETELY) similar to the sins like drinking,adultery etc which are major sins even if done once OR is it a minor sin but becomes major sin/Gunah Kabeera if done contionously?
Note:I have decided to keep a fist length beard so your answer will not affect my decision,but I am very curious in this matter so please answer my question.