Why would reusing a DataContext have a negative performance impact?

Question

After a fair amount of research and some errors, I modified my code so that it creates a new DataContext each time the database is queried or data is inserted. And the data

Answer 1

Even with a clustered index, in-memory lookup will always be faster than a database query--except in edge cases, like a 386 vs. a Cray--even if you factor out network-related delays.

I would guess the degradation has to do with the DataContext's handling of entities that it tracks: reusing a context will continually increase the number of tracked entities, and the call to SaveChanges may end up requiring more time.

Again, that's a guess--but it's where I'd start looking.