It will give you some respite, but not forever. Try to prepare the new line first, it should be shorter and behind rivers. Best to coordinate this with onset of mud season, so just as the Soviets will catch up with you, the mud will start, and they will be stranded with railheads far behind the front. This must be fairly long retreat like Dnieper to Vistula, so can be done only once, and only if your army is on the brink of destruction. Better to retreat, than suffer encirclement due to a breakthrough that you will fail to contain. Desperate measure for sure, but can buy some time. Worst option is to retreat slowly, so they catch up with you every turn. That way they replenish their troops better (no contact with enemy), while you can't do the same (since they move back into contact for your logistics phase).