splitting a big table

I have a table that is getting a lot of new records every day, and I 
can't delete old ones (for now). So I'm thinking of creating a second 
table, only store new data in my first and copy old data over to the 
second on a regular basis. I guess it's possible to manage both tables 
through just one entity, have some editing context delegate that check 
for queries to this entity and redirects them to either table depending 
on the dates that are being requested.

Before I dive into this, has anyone done something like this before, or 
maybe solved this kind of problem in a different way?


Thanks,
Christian