I have my e36 and rx7 insured as classic. E36 is my daily. No other primary policy. Nothing sneaky on my half. First Ireland in fact offered it as they knew I wouldn't pay 2200 for a standard policy.
1995 and 1991 so plenty old. A 2003/04 M3 might not yet be considered a classic in one sense which is why it would need a primary policy.