In our last house I accidentally used exterior gloss (sandtex branded to be precise) on the hallway stair rail, thing is it stayed durable when all other paint started cracking and thinning and it also stayed white when all other paint started yellowing. So.....

Is it safe to use exterior paint purposefully on interior wood? I've got 9 doors in the hallway (and all the architrave and skirting) this time to paint and don't fancy doing them too often. Google is giving mixed results

I would think exterior paint is less human friendly than interior but not sure.  Don't want to choke everyone for weeks lol!

Careful with glossing doors though, use a roller if you can, I redecorated most of Nans house last year, walls, ceiling, skirting all fine...but made a right mess of the doors!  Tried various brush techniques but they kept coming out patchy or full of runs.  In the end I left to it to my Uncle to do lol, apparently he used a roller but I'm guessing there's some sort of skill or knack to it that I don't have haha.

Like Tom said, I would've thought there was less of an issue with dedicated interior paints and noxious fumes and odours.  I don't think xylene is allowed any more, but you wouldn't want to paint inside with a xylene based paint and breathe in the house for a while

There are specific rollers for gloss paint, and indeed each type of finish. Although the paint pads can on large surfaces produce a superior finish, and you don't end up with 'highlights' matching your decor, in your hair, when painting overhead.

Everyone who I know who makes their own furniture, seems to spray gloss paint now rather than brush or roll.  But that's within the confines of a dedicated workshop, so it's not that helpful

Within the realms of rollering gloss paint (but not houses) I know of one chap who didn't want to learn how to spray. He rollered his VW van in 1-pack.  It wasn't a patch on spraying it, but it wasn't as bad as you might otherwise think, it should've been.

The 'fed' paint systems are supposed to be better still, I've not actually tried one so I don't know how true that is.  It would certainly be a lot less messy in theory, with your roller/pad being fed with paint.  Like all these things they'd probably be a pain to clean though