To 'recharge' catnip toys, put them in a little sealed Tupperware tub with some loose, dried catnip for a few days! Then take them out - they'll smell much stronger!
Five Good Reasons for Having Your Cat Neutered
Reduces fighting, injury and noise
Reduces spraying and smelling
Much less likely to wander and get lost
Safer from diseases like feline AIDS, mammary tumours and feline leukaemia