Hey Snowy,
First of all, let me just say, I understand the whole entire reasoning - on the surface, it's a sensible idea. Get rid of all those hassles moving in together has (learning how each other live 24/7, coping with being a permanent dweller of the house together, learning how each other work domestically, etc etc) before the marriage starts - in some ways this DOES solve a lot of the dramas newly marrieds all have - I just have to look at a secular newly marrieds forum to see how true that is!
However, you have to understand the temptation you are getting yourself into. I am nowhere near getting married, but my flatmate has become my boyfriend. All of a sudden, what seemed pretty easy (and pretty sensible), has become a major conflict in my heart. I WANT to stay pure, I WANT to keep everything above board (especially when I am leadership in a church), but living together has upped the temptation factor more than I expected (I thought, won't be any different, we've lived together for 2 years without it being a major hassle, it won't change now)... ha ha ha.
Do you know how easy it is to think, oh I could just cuddle up in bed with him for a little while, before I move to my bed? Oh, ok so I'm in my pyjamas, not that revealing (do you know how much a pair of pyjamas actually reveals - quite a bit, especially since I doubt you go to bed wearing a bra!), not that much of a deal? Oh, he's/she's in the shower - that can be a huge temptation, believe it or not. I've managed to keep out and keep dressed since we started dating, but EESH - I would never have thought of these extra temptations happening.
I know a lot of people who would say these temptations happen even when you don't live together, but think of having the temptation there EVERY day of the week, not just the day you see him. It is a constant battle between what is 'almost but not quite ok' (ie cuddling up in bed when you are about to go to your bed/wake up in the morning, wandering around in your pyjamas, racing around in a towel to pick up the towel in the linen cupboard you use for your hair that you forgot when you were going for your shower, etc etc) and what is 'completely above board' (waiting til immediately before bed to get changed into your pyjamas, getting ALL your stuff ready before shower, getting straight from your bed to the lounge, without saying good morning to him, etc etc).
Some of that stuff I said up there might sound a bit ridiculous, but believe me - they are temptations I've found, and had to fight through, and it's respect thing for my boyfriend - if I'm so determined not to have sex before we are married, then I shouldn't be doing anything that causes him temptation and 'desire' to have it...
I know this was a hypothetical thing for you Snowy, but those reasons up there are reasons I'm wanting to move out - I'm not even going to get into what it shows others in our church, especially those younger or more impressionable than myself.
The problem I'm having now is finding a new home, with or without flatmates. I'm being pretty strict about it - I don't want a flatmate that might tempt me to sin with my boyfriend. I've even had to ve-to a Christian girl because her idea of what a boyfriend can and can't do with you is different to my idea!
Sasch