Saying their mass needs to be lower to reduce orbit degradation is the opposite of true. Assuming two spheres of equal size, their drag and thus change in momentum will be the same at the same altitude. But if one sphere was made of lead and the other made of styrofoam, the styrofoam one will decelerate much faster than the lead one. So: lighter satellite of the same shape means shorter life span. But drag dies down roughly exponentially in altitude, so if they're at 1000 km, rather than 100km, that's not a super big factor.
