VARCHAR query

Hello. I am setting up a table to receive data from a PBX device. I have been told that the data can be up to 255 chars. However, in browsing some of it, I see that rarely is it over 80. There are a lot of records - we need to keep 30 days on line with about 300000 records per month. Updates will not be required and the field is not indexed. I was wondering if a VARCHAR field would be a good idea here. I dont know what the overhead is (ie, what my actual savings would be). Any experience/tips gratefully accepted. TIA, tom dorgan.