Hmm, perhaps there is always the other side of the coin?
Some plants just simply don't like to be repotted, they will sulk if it is done the wrong time of year.
I buy a lot of plants which are established on mounts, so they are fine. And potted into bark mix - I don't think/remember now if I ever had a bug or slug problem buying from my usual favorite vendors. I do not have to repot because of that.
But - plants which come in Sphagnum are moved asap into either different media or get mounted etc. But I don't do it because of infestations. I just don't think Sphagnum is a good medium in the long run.
Along those lines, Neofinetia falcata from a certain seller will be unwrapped immediately, roots inspected and planted into CHC mix. I have found rotten roots under an old layer of Sphagnum which was rewrapped with fresh Sphagnum. Not cool!!
I never, ever buy ebay, but that is just my own personal quirk. Once people get to know the good sellers, they get pretty nice stuff.
Heh, whatever works for you?