Bayer insectides - Carbaryl + Confidor

I use carbaryl for dendrobium orchids as the new cane growths and flowers gets really hammered by dendrobium beetles (stethopachys formosa) over late summer and in june as flowers develop.

I use confidor against sap suckers that really make a meal of any new growth. Particularily on Syzigiums.
My argument for its use is that when they are young they really need all the help they can get to flourish. Nothing worse than seeing a sapling ruined up by them.

My question is: from your experience (if you have had need for their use) what is the efficacy period, ie; post spraying how long does the stuff remain in the vascular system before the need to respray?

I reckon that Bayer dont advertise this point as they thrive on the consumers fear, therefore using more of their product than neccessary.
I for one have a tendency to nukem and when in doubt give them a hit. what are your thoughts? A