I looked at one of my domains at intodns.com and I got a "Your SOA EXPIRE number is: 3600000. That is NOT OK".
What is a good SOA EXPIRE number?
intodns.com (I love them) is an automatic service. It reports anything uncommon, which may or may not represent a real problem.
As for expire specifically, very high values rarely affect anything, and in some setups SOA expire is not relevant at all.
As for RFC 1912, it's suggestion about expire is just that - suggestion if one wants to play no-brainer he can just use the suggestion. If one knows how his DNS infrastructure works, he can decide himself, and any value he choose will not be violation of the RFC.