Orthene and mealy bugs

[cirillonb]

Unfortunately I have a moderate mealy bug invasion that I have treated with repeated sprays (weekly x3) of Bayer Rose and Flower that contains Imidacloprid. I am wondering whether I should switch to orthene soluble powder (my farmer's coop has a can) What is the experience with that product? Since it is in a sealed can, is there likely to be an expiration date or maximum shelf life that I can uncover?
If I switch, should I only treat infected plants or the entire collection and how often should I repeat? I have used Orthene in its outside garden form and was very successful against various difficult to kill critters.
thanks. Nick