Both.
For in-game time, if a party has to spend 4 months travelling up to the arctic for a two-week adventure, then spend 4 months coming back again, this causes various issues to arise:
- the meta-plot has had all kinds of time to advance (possibly to places I haven't even planned out yet!) - 8-9 months is a long time in a situation where major shifts can happen within weeks
- that party is probably now way out of synch with the other groups (I run multiple parties in my world, sometimes interacting) meaning they'll have to be put on hold until the rest of the world catches up with them; and as sometimes those "major shifts" I mentioned are the direct result of the actions of a party I need to know what the other parties have been up to
I'm well aware of this, but wandering monsters and random encounters are (in theory) a fact of life and it seems jarring to mysteriously not have any such during a multi-month journey; also I've yet to see any party enter any town without getting into some sort of trouble...and there might be a lot of towns to go through en route...

Teleport *should* only be a single-person spell, plus what said person can physically carry. Planeshift is the one that can take a bunch of people and has in my experience been the bigger headache - I ended up having to put some limits on Planeshift but have never felt the need to do so with Teleport. Again, I have to bang 1e's drum here; as it got Teleport right.
Also,when I talk about teleport as an exit strategy from a no-win situation, I'm only referring to the caster. The rest of the party have to rely on the caster to somehow get them out and-or revive them from death*.
The same applies to scry-buff-teleport: if the caster's the only one who can go, the strategy becomes rather (literally!) self-limited.
* - in an old campaign of mine, this is exactly what happened: a PC who happened to have a device of teleportation saw the party had got WAY in over its head (due in large part to their own ignorance of a bunch of very clear warnings), grabbed what looked like the most expensive gear he could quickly find, and blipped out to town; the rest of the party was dead within 2 rounds. He then used said expensive gear to pay for a wish to revive people and get them out...
Lan-"as long as there is one survivor the party can and will continue"-efan