1992 Subaru Legacy Stinky Brakes

Hi, my 1992 subaru legacy wagon burns up brake pads. I can smell them burning when I get out of the car after taking my girls to school, and I have even seen smoke rising from the hood after 2+ hours on the highway after I return to the city and park. I have to replace them every 7000 miles. I have also experienced extreme vibrations when braking at high speeds and when I take it in, my mechanic says to replace the brakes. He says they're organic pads and they wear really fast. They're the Akebonos, I believe, and are more expensive. They squeak when brake dust gets in there. He says the organic pads are what Subaru recommends. Should I use the metallic pads? Is it the brakes (I just had front and rear done) or something else? How to be sure? The smell is only when I've been driving very fast and brake at high speeds. I can smell it as soon as I get off the highway (maybe 15 minutes of driving) and return to the streets. This Subaru is fantastic and has never let me down. I LOVE this car. I feel so safe in it driving my kids all over town. I hope you can help me as I would like to take care of this car the best I can. Thank you.