As the others have already said, it depends what you want - you're going to have to be fairly motivated to do a 1000 mile round trip for 2 full days in the house, not to mention the cost - petrol and ferry as you've said. The potential income bit struck me too - France is a little awash with Brits trying to earn a living - have a look at the auto entrepreneur's group, especially Emily Monté's experiences in Brittany and her thoughts. Having said that, if it's your dream and you want it to work and have the financial backing to make it work, then it will. There's nothing worse than saying I wonder what would have happened if we'd ... sometimes you just have to go for it, but knowing the full picture firs tmakes the leap easier ;-)
I think what Valerie has said is true, especially the bits about letting other family members use it from time to time and the bit about the house and trip not becoming a chore.
I would also say you need some reserve to pay things like the tax Foncière and for minor maintenance while the house is not occupied. I am sure there are plenty of people in the area who will offer their services to keep an eye on the property for you.
Best
I'm not in a position to advise as I bought our house as a permanent home but I'd just like to say what a good question I think it is.
There are numerous holiday homes in the hamlet I live: one stayed in for approximately 2 months per year and a second and third for possibly 4 weeks each. The first is used by various family members at different vacation times so is put to shared used (good idea), a couple own the 2nd house which is barely used and they are thinking of selling (well, he is and she isn't) and the 3rd house may only be used for short periods of time but is thoroughly enjoyed by a family with children.
If you enjoy taking, say, 3 holidays a year but prefer 2 of them to be flying to the US and Spain, you won't be enthusiastic about making the trip. If it becomes a chore, you won't bother. If you simply love France and want to pop over to your 'sanctuary', you will.
By the way, are there any 'cheap' flights near your area in Brittany that could come in useful for short hops?
We’ve had the house that we live in now, for 18 years but before that had one in Picardie. We lived then in Leeds. Our optimum time, door to door in those days was 7 hours and 40 minutes, but thst was unusual, and it usually took us about 12 hours. Our kids were little and we probably went at least 6 times a year, but for a minimum of 1 week, and often for up to 3. So, over the 10 years we had it, we made very good use of it. Costs were a lot cheaper, so, you need to be reslistic about how much time you can or want to allocate to it. It’s all to do with what it means to you.