So last Christmas, Oliver got a catnip mouse toy from his kitty sitter... it's maybe 3 inches long made out of leopard print, fuzzy fabric - it came with a tube of catnip and the mouse has velcro on the bottom so you can refill the catnip... well I've NEVER seen Oliver react to catnip the way he does with this toy... my question is: how often should the catnip inside be replaced? I haven't replaced it yet since he first got it (I didn't out the entire tube in the first time - it wouldn't have all fit anyway)... he still goes crazy over it occasionally, but I just don't know how long the effects of the catnip last... also, any tips on getting all (or most) of the old catnip out of it? Thanks!