You don't say what lilies you have, but I will guess they are probably Asiatics. If you withhold the water you have been giving them they would probably remain dormant until you do water them. I am not familiar with your climate but am guessing it will get too cold for them to survive growing through the cold of winter. Al

Yes, they are Asiatics. I was concerned about the heat and them drying out so that's why I kept watering them. It's been 100F+ through most of the summer. When they were left in the ground last season, they stayed dormant despite still being watered regularly by my sprinkler system.

But for the ones that are growing, will it hurt the bulbs if they sprout this second time and die in the winter? Will they still be good for next spring?

Some will probably be lost that are growing now as they are using the energy stored in the bulb. Can you not move the container to a cooler place, like a dark basement? Al

How brutal are your frosts?

What I notice is that the small asiatic 'pips' tend to throw up leaves over the winter which will easily cope with frosts down to -7C while the big bloom-ready bulbs hide out until spring.

No matter what I do this type of lily bulb keeps coming to the surface. In response I cover it thickly in autumn with good compost which gives insulation, feeding, and frost protection.

They often do better in a situation where they grow among sheltering deciduous shrubs - better drainage, leaf litter, protection from winds, and root shading over summer but still able to get good sunlight to stop them going straggly. Like Clematis.

If you have a site ready-dug and amended you could gently shake out your container, move some of the bigger bulbs into the ground and mulch for protection - then put the remainder into new or refreshed mix in your container as insurance against a quirky winter.

Asiatics often naturalise so I don't think they're too fragile. They do like that annual top up of compost, though. More flowers and sturdier stems.

I agree with vetivert. I am not a big lily grower, but I have had Asiatics. They are so vigorous here that they can get to be a nuisance. They definitely will put up leaves in fall that overwinter. It doesn't seem to hurt them. If you can, plant them in the ground. They'll do better in every way. If you cannot, then listen to Al and bring them inside at least on really cold nights (which are probably few for you).