Alfalfa & Timothy Mix Cubes?

I have 8 show rabbits, and have only ever fed them pellets. I decided to start hay, but wanted to do cubes. I bought Alfalfa and Timothy Mix Cubes, and my rabbits range from 2 months to 5 years old. I read that Alfalfa is bad for rabbits over a year old, and I cannot have my rabbits go overweight. I am not interested in buying just Timothy, much too expensive here. I feed bales of Oat Hay to my sheep, and I was wondering about it for my rabbits too. I haven't started feeding the cubes yet.

The long strands of hay are what is so good for rabbits. The cubes are more for entertainment.

You are right that alfalfa is for younger rabbits. It is a legume (not grass) and far too rich for adult rabbits (over 6 months of age).
Timothy hay is a grass hay but isn't your only option. Any grass hay (including oat hay) is fine for feeding to rabbits of any age every day.