Yes always, we've only once had to separate them and that was at the vets because Blossom kept chewing through Rodney's IV line. But even then they kept her in the kennel opposite and put them back together once his IV wasn't needed.
When returned to me they made sure to tell me how badly behaved he was without her whereas usually he's a very good boy at the vets.
These days with car park drop off I put a note on the carrier of which ones which if its not our usual vet. Occasionally a nurse asks which one is having treatment but if anything I've always had good comments about it.
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