There is no minimum Rehit for keeping Sarbloh Bibek. All Rehit is mandatory for Gursikhs and they strive to keep all Rehit of Guru Sahib.
Having said that, it does not look good if a Sarbohi Gursikh does not get up at Amritvela and do Naam Abhyaas. All Rehit is kept in order to enhance one's Naam Abhyaas and if one keeps Rehit but does not engage in Naam Abhyaas, then one is not fully obeying Guru Sahib's Hukam. The foremost Hukam of Guru Sahib is Naam, Naam and more Naam. If we don't obey this Hukam, then we won't get Kirpa we are looking for.
We should strive to keep Rehit, obey Hukams of Guru Sahib and engage in Gurmat Naam Abhyaas Kamaaee.
Kulbir Singh