My 2 cents on quarantining plants:
Putting anything in quarantine for a while is never a bad idea. If I get plants from someone I don't know, I do a potassium permanganate dip and then quarantine a week or so.
If I know the person, and have received countless boxes of plants from them, I might do the dip and then go ahead and add to tank.
Plants from overseas DEFINITELY need a quarantine period. I have a buddy who killed a whole tank of shrimp just by adding plants to a tank he had rinsed off repeatedly. There was still a bit of bromide gas residue on the plants after all that rinsing, which was more than enough to kill every single shrimp.
If you aren't on a first name basis with the owners of your local pet store, I would quarantine their plants as well. Even if I were on a first name basis with them, if they had plants in tanks with a central filtration tying them into other tanks with fish, I would still dip and quarantine.
Even if you trust the person or people you're getting plants from, that doesn't mean that there is no way they could unintentionally give you something you don't want, as in icky diseases, carnivorous larvae ( dragonfly nymphs, etc.), pest snails, duckweed, etc. Dipping and THEN quarantine is usually your best bet. A plant shouldn't mind a couple of weeks or so by itself.
