When to lift and divide snowdrops

I have numerous different varieties of snowdrops, with some flowering from gathered seed. This means that some came into flower at the end of December, whilst others are only coming into their own now....

So, to those experienced in division, how long after the flowers have finished do you lift and divide clumps of snowdrops “in the green”?
- when the flowers go over?
- when the browning petals fall off?
- after the petals have gone, and the seed heads have swollen?
- when the seed heads are bent down and touching the soil?

They are one of my favourite flowers, so I want to increase their numbers as fast as possible...

I'm also planning on trying to increase my tête-à-tête daffodils in a similar manner - it’s just so much easier to do when you can see all the bulb-growth and planting in established beds. Has anyone any experience of doing this?

 

Any time when the ground is not frozen is ok. Best practice is when the leaves have gone over completely, but not always possible. I have just split some clumps this morning.
Same for Narcissus.

 

Snowdrops divided ok when in the green, as in with leaves still growing, so as palustris said anytime when grounds not frozen

 

Well, the sunshine beckoned outside, and the large clumps of snowdrops have been lifted and replanted within about 30 mins of coming out of the ground, so they should not have dried out. About to go around and water them in, as we have no rain forecast for the next 5 days...