Without railroading, how can the DM force you to leave your base?*
And once you get mid-level transportation magic, how can he stop you from going to-and-fro?
* Not considering, of course, the metagame, "Hey, guys - I'd like to run an adventure where you travel to [etc.] ..." method.
He can't force you to leave you base you can sit there all nice and snug while the bad guys have free reign over the world. Or he can say since you guys don't want to play anymore today lets wrap the game up.
So you clear out an area of the dungeon and teleport home to your bed I hope you are ready to clear out that level again because your handy work has been discovered and now they are ready for you.
The king hired you to rescue his daughter instead of paying the ransom but instead of continuing on you teleport home to sleep in a comfy bed. Meanwhile your activities have been discovered and the bad guys realize they king does not intend to pay so he sends the king his daughter's head. Now the king has a bounty on your heads.