Honestly, there is no evidence of enzymes like RidX have any benefits. On the contrary, it is evident in field work that enzymes can cause problems like drainfield clogging due to over breakdown and microorganism overgrowth. Yeast is the fungus candida which is a bacterial competitor. Adding bacteria can have the negative effect of either overgrowth or cannibalistic waste, both add to the solids in the tank.
If you really want to extend pumping intervals, eat more yogurt, use 1 ply toilet paper, cut back on all chemical use including detergents, and allow NO grease to enter the tank (including grease and oil on clothing and body).