I have 2 nationalities.

If I did back to back single entry tourist visas , or visa exemptions. I can then extend them for a month. Then keep flying in and out and switching passports?

Or are they on top of that?  Its just to the discretion of of the officer. So if I do 2 or 3 SETV (then extending each by a month) then fly out and fly back on other passport. Possibly I could fly out to a country that doesn't have passport stamps and back in on the other then I can say I came from X country (without lying) and give them the next passport. This makes it not suspicious that theres not an exit stamp from country I came in from. So basically doing the passport swap in a country that doesn't put stamps in passports then using the next passport. 

 

 Im not suggesting lying and say I got off a different flight from my home country 

 

Any ideas thanks

There’s no advantage when entering the country. They will almost certainly link your two passports and the IO will see your combined history. 
 

Whenever you present your passport the system searches for any name, dob, etc. matches. It’s then up to the IO to manually link any passports of the same or different nationality.

 

It could help you getting visas because the embassies/consulates, that apply limits, go by the number of visas they see in your passport.

Following

Biometrics will reveal that you are the same person. My guess is that this will create more problems for you than the ones you are trying to solve.

2 hours ago, Tuvoc said:

Biometrics will reveal that you are the same person. My guess is that this will create more problems for you than the ones you are trying to solve.

I would think the same.

It will help getting out of the country quicker if things go tits up 

It will probably won't work because of fingerprinting then your are left looking bad trying to game the system.