One way to test the validity of the proposed and controversial term-limitation bills might be to ascertain how much a congressman's negligence or venality is influenced by length of term.One way to do this would be to examine the records of our congressmen to determine how many of those who have served in Congress for more than 12 years have committed such irregularities as bouncing checks at the House bank or leaving restaurant bills unpaid. This figure then could be compared to the number of newer congressmen who have made the same indiscretions to see if there is a discrepancy. Statistics such as this would, I think, help us better determine the need for a term-limitation bill. C. Freeman Keith, Lancaster, N. H. Letters are welcome. Only a selection can be published, subject to condensation, and none acknowledged. Please address them to "Readers Write," One Norway St., Boston, MA 02115.