It's up to you ... obviously a warranty is a nice thing to have. I tend to update either the group or the frame when I feel the need so my last two changes have involved previously-loved frames (both Roubaix too). My current ride is a 2012 SL3 Expert (threaded BB thank you very much) and it's been perfect. It was a very large upgrade from my 2007 Roubaix and I have no current urges to upgrade it at all. I think I got the frame for $1136 on fleabay, which is obviously significantly less than a bare frame would have cost from Specialized, so the lack of warranty isn't bothering me.