Over a minute and a half to cut two 1 and a half in branches while using plenty of energy.The idea is better than a just having a saw(the bow),the saw will still only last a few cuts though.
If you want a real tool get a good quality hatchet or axe.It will save energy and prove much more useful than any saw.The durability and usefulness of an axe or hatchet is worth the weight in any survival situation.