Lily bulbs

A loooong time ago I bought some yearling lily bulbs and planted them in an old copper. I really didn't expecy much in the way of flowers for the first year, but I had the most glorious display, one flower per stem, but imagine a dozen blooms close together, all open at the same time and about six inches across. Show stoppers.
here's a photo

https://trademe.tmcdn.co.nz/photoserver/full/723933574.jpg

My question is this. Are lillies like spring bulbs, need to die back before digging, or cutting the stems. I want to use the copper for something else.
I know if I dig them, that they will need to be replanted to keep them moist, not like spring bulbs that can be left for months in storage.

Leave the stems on after flowering. The goodness goes back into the bulb. They take a long time to die back. That’s when you should transplant them. Don’t leave the bulbs exposed, repot or plant in the garden straight away. Feed with bulb food

Better to remove the spent flower heads unless you want to collect seed, the stem should be left to die off, and provide nutrient for the next seasons flowering, however it probably wouldn't do any harm to transplant the whole contents of the tub into the soil somewhere. then you can reuse the copper.

so as I thought, I've really put the copper out of commission for a while, because there are twelve bulbs planted in that copper and getting them out will not be easy, although I guess I could try one. Trouble being that they may have made a huge root ball.
I never expected the result I got, but also know that for the second year, they don't do so well in potting mix. I've grown too many bulbs that way to be hopeful of taking out bigger bulbs than I planted.
I'll do one, or two, and let you know how things go

Thankyou to the ladies who have responded. I really KNEW what the answer would be, just hoped it would be a bit different

addition
Well, that was a mission and a half. The roots on them were amzing. The last four came out as one huge clump. the others came out singly, plus a few wee bulblets that I will give to my home help lady.
NOW I have nowhere to plant them, will need to go and buy some bigger black pots tomorrow, if Mitre 10 have them. Otherwisde there will have to be a major reshuffle of plants in pots, to make room for 12 more.
Oh to have my two acres back again, instead of about 200sq m with a 65sq m house on most of it. AND leaving room for the van. Oh well, the penalty of growing old I guess.

I love your display Colin, I grew these for the first time this year. Very pretty.

hope you dont have cats wandering around with these on the ground as the pollen kills cats

no cats here bobcat, and anyway I remove the ends off the stamens so the pollen doesns't stain the petals, especially the white ones.

I managed to get them all out of the copper, WHAT A JOB! They had huge roots. Lost just one stem, so did pretty well. I can't remember how big the bulbs were when we planted them, but pretty sure they have increased in size which is good. There were even a few little bulblets, or do you call them bulbils. Replanted on the periphery (spelling doesn't look right) of the feijoas in a garden on the boundary, so hoping for a good display again next year. The other lillies are also planted in that area for them to grown on in SOIL for a year, then back into pots for the next season.

My lillies (orange in colour) have just multiplied over the last couple of years and have now filled the two outdoor planters along our deck. The display this year was amazing. They are such beautiful flowers.