certainly cut the older leaves but leave a few of the inner ones untouched so that it has reserves for next season. I rarely find mine fully die back.

Mine do not die back either so I tie them up to shelter the next flowers and cut off the excess and compost it. In the Spring I untie and strip off any unsightly leaves and compost them too. I found the rotting vegetation disgusting if I did not treat them as I do. An old council gardener told me they treated them this way and it works well for me. I had to search but if you look at Page 32 of my photos there are two photos 30 and 31 of kniphofias flowering and put to bed for the winter.