I thought that Alfalfa pellet is more for baby and mommy chins? Then Timothy is more for the adults?
Well actually now that I think about it...that's how it is for rabbits. Maybe I have things confused. 
I guess I need a pretty even balance between the two then?
For chinchilla, most of the pellets are alfalfa base, adult chin should feed on alfalfa base pellets as well, which the Crude Protein content should at least 16% (some pet owners even said should not be less than 18%)!!
Normally, timothy base chin pellet os used for some over weight or elderly chin only, and the Crude Protein content is less than 16%!!
Rabbits and guinea pig is a bit different, adult Rabbits and guinea pig (> 6 months) are feed on timothy base pellets, it's only the normal situation, it can be depends!!
If there is any misunderstanding, experienced pet owner / breeder can point out, because that's the normal practice at my place!! I would like to know if there is any other different opinions as well!!