I have 6 months of data, how do I replicate only the most current 3 months of data to the subscribers?Answer1:
You can use filtered replication. When you read examples about filtered replication, you'll probably see it referring to a branch office scenario where a single central office stores data for several branch offices, and each branch only wants to replicate their own data. It involves creating filters on a key, and in your case, you'll want to use your date range as the key.
Here's an <a href="http://sqlserverpedia.com/wiki/Creating_Transactional_Replication_Publications" rel="nofollow">article on filtered replication with transactional replication</a>, and another on <a href="http://sqlserverpedia.com/wiki/Creating_Merge_Replication_Publications" rel="nofollow">filtering with merge replication</a>.