Rescuing vehlis can be done in 2 days as you only need to do 3 things
1st day: go to fortress talk to everyone and use the magic scan thing on fortress, then return to elf dude and talk to him about what you scanned(this should unlock a secret room) and go sleep
2nd day: talk to elf dude to recharge your magic scan thing after which you go back to fortress and go to the new room and search it, talk to everyone in town, then go back and scan the room in the fortress after which go to the apothecary he/she should have a potion ready to buy, buy potion and then go back to elf dude and tell him what you found out which should unlock the "let's go rescue Vehlis" option (note: you need to potion to succeed), finish the fight and then your done