So my thoughts on this are that the use of portals don't stop exploration at all. They stop the need to run back and forth between destination and rest area. After some distance of exploration, it actually becomes fairly prohibitive. It doesn't shortcut the danger. It just shortcuts the exposure to the number of times you're exposed to danger while doing things you don't want to do anyways, such as moving across the map. The actual danger is ever-present.
I know that I'm kind of a newb, but for me, the inability to use portals for moving metal is a hard limiting factor for how far I'm willing to go to find it, especially without a way to shorten the distance, such as with a mount.
The other option is that I can just move my base with a cart every time I outgrow an area. That would be fine too. Need bigger carts though. That's not exploration though so much as just never having a home.