I am relatively new to bicycle commuting, but recently searched for and purchased a rack and set of panniers. I, too, wanted something that was sturdy and would last. I ended up purchasing a Tubus Cargo rack and a set of Ortlieb Back Roller Plus panniers. While these things were expensive (they cost more than my "beater" road bike I put them on), I am confident they will last a long, long time. In fact, if/when I upgrade to a nicer bicycle, I will be taking the rack and panniers with me.

As a plus, my rack is made of steel. If it breaks, tubus has a great warranty, OR, I can get someone to weld it back together for me. I'd be a bit leery of using aluminum; although, I know many here have no qualms with using aluminum.

The rack/panniers I chose may be a bit out of your price range, though. Cash is tight, but I like nice things. Good luck in your hunt!