How long can you keep plants in their garden centre container (Small Pots) before transplanting in to the garden soils?

After purchasing bedding plants from the garden centre. How long can you keep them in the greenhouse before transplanting them in to the garden soils?

Plant them ASAP. The sooner you plant them, the quicker that they can get growing.
There is a brief period of slow growth and adjustment by each plant I would imagine, but buying them and leaving them in those small packs, sooner or later has to adversely effect them.
But a week or ten days wouldn't hurt them too much.

Thanks for your help. One other point, the plants have what appears to be "Binding" around the soil which moulds the compost. Should this be loosened or, clipped away?