My mum used to say "if you want to keep your friends don't go on holiday with them".
I've done it a couple of times with my best mate, but never for more than a week so we never reached the stage of wanting to hack each other to death. Much as I love her, she did drive me crackers.
My mum also ignored her own rule by going on holiday with her oldest friend. They'd know each other since they were 14 years old, and when they were about 65, they went to South Africa together for a three-month visit to Friend's family. They had to share not only a room but a bed, and after less than a month they began to realise how different they were.
They wanted to do different things, go to different places. Friend only wanted to go round the shops and my mum wanted to see the country, and if my mum and the son went exploring without Friend then she moaned about being neglected.
Everything about them started to grate on the other's nerves, and they barely spoke to each other for the last couple of weeks.
When they got back they never ever spoke again, so that was more than 50 years' friendship down the drain, all because they realised that at close quarters they really couldn't stand one another.