The group could continue harvesting resources from the outer edges of the forest since that was still officially a fourth level danger zone, while the depths of the forest were a fifth level danger zone. But there was no telling when the entire forest would be deemed a fifth level danger zone. So without holding anything back, the group continued training and harvesting resources like crazy.
There were a few occasions when they went to the guild where people wondered how a third level mage could consistently bring back materials from the forest where not even fifth level mages could guarantee their safety. But as long as the materials they brought back were from the fourth level danger zone of the forest, it would be fine as long as the danger zone isn't upgraded. And it looked like that would happen sooner rather than later.