OP, you can easily wait longer on the oil, and from my studying here, I'd say you're actually doing the car a service to wait longer...7-8K miles is great. I just did 10.7 and was fine...BMW says 15.5K miles...all assuming you use an LL-01 oil, of course.
Mango's right about the ET failing, and cooling system is a great way to invest money. Thermostat is seemingly more likely to fail than ET and WP, but eventually everything will.
You can also wait for things to fail and spend money when you have to, but you'll have to pay for a tow truck also. Life is a gamble!
Sounds like you'll be good at this!