Whether they might not have been more rapidly extricated by keeping to the original plan is a question which will long furnish an excellent subject for military debate.

Had Buller in November known that Ladysmith was capable of holding out until March, is it conceivable that he, with his whole army corps and as many more troops as he cared to summon from England, would not have made such an advance in four months through the Free State as would necessitate the abandonment of the sieges both of Kimberley and of Ladysmith?
If the Boers persisted in these sieges they could not possibly place more than 20,000 men on the Orange River to face 60, 000 whom Buller could have had there by the first week in December.

Methuen's force, French's force, Gatacre's force, and the Natal force, with the exception of garrisons for Pietermaritzburg and Durban, would have assembled, with a reserve of another sixty thousand men in the colony or on the sea ready to fill the gaps in his advance.
Moving over a flat country with plenty of flanking room, it is probable that he would have been in Bloemfontein by Christmas and at the Vaal River late in January.

What could the Boers do then?
They might remain before Ladysmith, and learn that their capital and their gold mines had been taken in their absence.

Or they might abandon the siege and trek back to defend their own homes.