Best if you can leave it 4 weeks at least between flowering and cutting down.

Don't know what your leaves look like but mine were hardly green this year due to the dry weather. It will be interesting to see what they are like next year as I suspect there won't be a lot of goodness going back into the bulbs from such sorry looking leaves. Last year I left mine on until they looked dried up. I pulled at them every so often and only took off the ones that came away easily. If they were resistant I left them until next time and eventually they were all removed.

Mine were fabulously green, but only because I had the sprinkler on every week for 40 minutes at a time. I did cut them right down after 6 weeks, but mine were finished by early to mid August.

Mine did try, but failed. Needless to say there were very few flowers this year !!

Wonderful show up here - but then - no water shortage and some are still in flower.
I leave them for the birds to enjoy the seed heads....but then I am a lazy gardener!