How long can/should a primary key be?

Could anyone tell me about things I should consider when defining a long primary key. We have a location table which will be 32 characters in length. The key will consist of an account number, and several address elements (house number, zip code etc.) What is the maximum length in bytes that a primary key can be? One consideration I can see is that it will take longer to drop and recreate indexes; is there anything else I should consider. Also, are there pros or cons for having a VARCHAR field in a primary key?  

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Rosemary Fleming 
Database Administration 
Toronto Dominion Bank 
flemir_at_tdbank.ca