There's really nothing to worry about on a 'high' milage WRX, the 2004 one i linked to has only done 9,500 miles a year.
Parts are so hilariously cheap on those things milage really isn't a concern as long as the body is in decent shape, break a gearbox? £200 for another, new up-rated discs and pads all round? £235 etc etc
Really?
I was having a good read through a scooby club forum and people was spending thousands up on thousands over a year fixing their scoobys.
Think they was STI's i was reading though, so a different story i guess?