Heh... I live 2 miles from work and really kind of wish I lived further! I'd take it as a mixed blessing. If you're riding a lot you should have no problem with 24 miles (even twice a day).
Sounds like you're pretty prepared my main advice is to get everything you need on the bike the night before and double check it. Lay your clothes out and don't think about how far you have to go just get on the bike and ride!!
Good luck!
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2009 Bike Friday Season Tikit (commuting folder)
2007 Rivendell Atlantis (touring, general riding, errand runner, stuff hauler)
2007 IRO Mark V (SS)
2006 Rockhopper Comp Disc (Icebike)