I'm 6'3" & 200lbs, so the wrx seats currently fit me pretty good, the legacy isn't too bad either. The knee issue is why I've chosen the 2 types that I did. I've been in outbacks & forresters, not impressed.
I'd be planning on at least 4-6 years, long enough to pay it off and replace my daily driver, unless we love it and it's not costing us a payment to keep running. The subaru will be my wife's commuter while I drive it weekends and evenings. It will probably see 12k miles per year, that's what we're doing on the SUV, but it may get driven into the mountains more. We aren't planning on anymore kids, at least anytime soon, so we should at least get through the planned life of the car.
As I stated above we currently have 2 vehicles, so heavier DIY store trips won't be an issue, I have a mid-size truck and access to a 3/4 ton and trailer for those really expensive runs. I just want to make sure the WRX (since it's slightly smaller) is quite liveable day to day if we go that route. Our last 2 purchases have been somewhat rushed due to circumstances and we didn't quite get what we wanted, but it filled a purpose. This is really starting to sound like do we want to have a light fast and fun car, or a slightly larger still fairly fun with a lot of toys inside car; we do like the memory seat in the legacy, as their is about a foot difference in our heights, though the wrx seats are quickly adjusted.