Before using as a counter electrode heat treatment always a better option 

While heat treatment will always remove inherent stresses and make the electrodes less vulnerable for corrosion, for day to day and mundane uses as counter electrode this may not much.  If you have facilities and you can afford it heat treatment will help

Hi.

In my opinion the best counter electrode must be inert such gold, platinum and stain steel as well.

Recommendation for the best counter electrode depends on the pH of the solution, the type of reaction expected, the pH of the solution  and the corrosion properties of the metal. Pt and Au can be good for most reactions, but even glassy carbon can be as good if some anions like Cl- or Br- etc are avoided.

Yes glassy carbon can also be used for counter electrode. Inert electrodes Stainless steel and nickel also used for counter electrode.

Thank you all for your inputs. They have been mostly invaluable. I am very grateful. 

Why do need Ni as a counter electrode instead of normal Pt or graphite? Is there any specific reasons for your studying systems? For example, for low cost. Ni is still considered as among active metals. The heat treatment of Ni could produce Ni oxides on the surface and in turn reduce the conductivity, which is normally not desirable for a counter electrode for conventional electrochemistry experiments. In basic solutions (pH > 12), Ni will be stabilized but the Ni hydroxide layers are formed on the electrode surface. However, if you mean the energy devices, Ni has been widely used as a current collector.  

Why do you need to use Ni as counter electrode? for what propose?

This is unusual counter electrode. as I see, you are in USA. So, it is not a matter of the cost? 

Hi Alaa, Indeed you are right! It is not a matter of cost, it is a matter of forming a geometry with a high surface area

ok, and for what purpose you need a counter electrode with large surface area? how large?

because you can use Pt net or Pt deposition on graphite sheet

@Alaa: We have Pt in the lab, graphite and all the other possible counter electrodes. Nickel works well for the purpose we want to apply it. The advantage here is that it can be contorted -you can't do this with a Pt net- to a high surface area material.