How long can trees last without being planted?

My husband spent £800 having four 8ft high hornbeam trees delivered. Their roots are in a sort of hessian ball.

The trees were delivered about three weeks ago and he still hasn't planted them. He insists they're fine but we've had several nights of sub-zero temperatures, lots of rain etc. Are they really ok? I don't know about these things and we couldn't really afford the £800 anyway, so I really don't want them to die.