It seems there are mixed results with different lower voltage kernels.
I think there is no "one size fits it all" solution as everybody has a different chipset quality
and different usage pattern.
for example, for me the latest XLV kernel worked perfectly with very low battery discharge.

My current plan is to replace the different kernels with a single kernel that can be configured while running. This would mean less maintenance for me, easier installation (from extras) and no need for reflashing.
In addition to min/max frequency settings it should have an option to select a voltage look up table
(normal, LV, ULV, XLV) and the possibility to disable some frequencies in the table
(e.g. 250 Mhz to get a permanent minimum of 500). I'm currently investigating whether this is possible.