I say, if you've got 48 hours in Lima, you can easily spend the time eating and drinking. Try a real Peruvian pisco sour, enjoy a good ceviche for lunch at any one of dozens of good seafood restaurants, and dine well at night. Check this forum for previous discussions on Peruvian cuisine. Lima is the capital of Peru and the capital of good eating in South America, IMHO.

In between meals there's lots to see in Lima including the colonial center of old Lima (there's one day right there) as well as museums, shopping, etc. Be forewarned, Lima is a gritty-looking place, including the first bit of it you'll see in Callao near the international airport, but it's still a fascinating city with a lot to see and do.