In DnD, this mechanic is always debated and stressed over by DMs. One suggestion is always to just give some sort of tradeoff when resting, and make it apparent to the player. It would be really interesting if there were consequences to resting excessively. It's still early access, so maybe Larian has something in the works for this.
Spoiler:
As for the tadpole, it seems like the diminshing of urgency is done on purpose. One night, talking to the mage character, he mentions that it's day 2 and we should be seeing the effects of the metamorphosis by now, and is confused as to why we are not.
Another way to deal with resting too often is choosing WHERE you are resting. If you hit the long rest button in a dungeon, maybe the terrain should be different, maybe even taking place in the dungeon itself, so you would need to find a defensible position. And then you could have monsters in the dungeon try and ambush you as you rest. This would add an element of danger to resting.
You could also make resting have penalties from your companions themselves. They could call you out for resting too much, saying you are wasting time, and maybe even refusing to adventure with you further and leaving the party.
