If it's a color I like, I wouldn't care if it's from 10 years ago lol. As another poster mentioned, there's no leftover B or K. Those bags sell themselves, and if you pass on 1, someone else will snatch it up for sure.
For myself, I usually buy colors that I like regardless of season. I also find that some color looks better on one style than on another. Sometimes I'd pass up on in-season color bag if I wasn't attracted to it. I know my mom, who lives in Asia, is more concerned about colors/styles that are in-season so she'd only buy things that are either in season or classic.
If you like RT then go for it. I think it looks gorgeous but you have to like it. G'luck!