Take it from this angle,
You enjoy the car, Yes you have invested a great deal of money into it but I assume that you didn't skimp on the quality of the parts that you have put in, therefore you should get a huge amount of mileage out of it without incident.
Cars tend to 'wear out' in fazes, some cars will do a huge number of miles without anything going wrong, others will seemingly need constant repairs, but if you are able to get replacments done in batches i.e. all the suspension components, the brakes overhauled, the engine work done. You will find that you may well spend a lot of money in a hit but those items will not require replacement for many many miles. I am just about to spend $6K on full overhaul of the Automatic Transmission in mine, when I talked to the Wife she never even batted an eyelid about it. We just 'had' to do it as she loves it (even though she is dead set scared of driving the car!) as do the kids. It's funny this car has affected the whole family.
Sorry I digress........
I also think that if you do a lot of short hops say less than 15 miles a day in a trip all the time it car never really gets all the components up to their full operating temperature for an extended period, this can lead to premature wear and tear.
Here's an idea,
If your able to, take your Wife with a picnic lunch and your car and go for a day trip every couple of weeks if you can manage it. The day out with your Wife will be appreciated by her (you probably won't get any grief about a day out even if it is in the car, the picnic lunch will help here) and you will get the joy of driving your car for an entire day. This will help to keep it in good condition as it is getting everything nice and hot, your car will thank you and your Wife will thank you and what is more you will be happy and you may kindle the affection that most people here display in one way or another for their 'special Bimmer'
Like Paul said, 'I think you know the answer'
Cheers!