Cuttings. When to remove the bag?

I’m experimenting with cutting sand I’m 3 and 1/2 weeks in. Some look ropey but I knew I was taking a pint with timing and some are in perfect condition. At what point to I do away with the zip lock bags?

 

When they are rooted, would be my guess, and then slowly acclimatise to dryer conditions.

 

I took some cuttings of verbena Bampton about a month ago.
Having trimmed all leaves back to a few mm - potted in gritty compost - watered - then into a bag.
I opened it briefly every few days to freshen the air inside and a few days ago I noticed some side shoots appearing.
No sign of roots from the bottom of the pot yet, but they're out of the bag and on staging in the greenhouse now. New leaves are sprouting too now.
When I see roots coming out of the bottom of the pot, I'll knock them out and plant up seperately.

I took 12 penstemon cuttings yesterday and I'll treat them the same.

 

It also depneds on what the plant is, as well as your growing conditions. They often don't need those bags at all.
You have to be vigilant with them though, if you use bags, and check regularly. Some will strike quickly and some won't.