Base the forms and reports on a query that uses a parameter in your
DateField:
DateAdd("yyyy",-3,[DateField])
This assumes you are using forms, and that you are not entering data
directly into tables. Even if you are entering data directly into tables
(which you should not be doing), you can use the query instead of the table.
You won't see records from longer ago than 3 years, and it will look just
like a table. A better choice if you like the look of a grid would be to
make a form based on the query, and to set its default view to Datasheet.
Unless your database is approaching the 2GB limit, or there are performance
issues that can be attributed to the size of the table (and that cannot be
solved through improved database design), there is probably no reason to
move records to another table. If it is approaching that 2GB limit the
other table will have to be in another database.