I would stop using them if you can see those rivets. In my experience, the pad wear accelerates as the pad gets thinner and thinner.

Are you using XR1s or XR2s?

 

+1^^^
If Cobalt's rivets are like Carbotech's rivets then you should change out the pads ASAP because you are about to machine some nifty grooves into your rotors. Out of curiosity, can you (Zefiris) take a measurement of how much pad material is left?

 

So picture time. This first picture is a set of XR3s. When I first ordered Cobalts, the guys at Adrenaline recommended a XR3/5 setup. The 3s weren't quite up to it though.



^This pad had the most material left. 6mm tapering to 4mm material left.

This next picture is an XR1. After the 3/5 combo was done, I switched to a XR1/2 setup. Felt much better. I only got about 7 days out of these. I had just put on brake ducting before the 7th day, so hopefully the pad life will be better with the extra cooling. There was a vendor there at Chuckwalla that happened to have some Hawk Blues that fit. Much more pedal effort required compared to the Cobalts, but still stop the car. The Blues seem to fade a bit after about 3-4 laps at Chuckwalla. Found out later the Blues are only rated to 1000F.



^ XR1, about 5mm of pad material left. Even on the most tapered one with 2mm of pad material left, I don't feel any grooves in my rotors. I didn't realize they were that low until I took them off. Thought there was much more pad left when I started the weekend.

 

You needs wilwood. If you're going through pads in 7 days, you need to get rid of pad taper by buying wilwoods, you'll gain quite a bit of pad life.

 

Unfortunately I'm out of points if I want to stay in TTA. If I step up to TTS, the brakes will be the first thing to get upgraded, followed by suspension bracing.

 

I was also recommended xr3s when I first got Cobalt pads, definitely not aggressive enough for a turbo miata. Personally, I really like XR1s but an XR2 might work for lower HP (~160-190whp) guys.

Lol @ 7 weekends from a set of pads. I go through 1.5 sets during an SCCA Double National weekend with my heavy, underbraked SSB car...

Heck, I destroyed a brand new set of XR1s during the runoffs race (i.e. 13 laps at Road America). Our rear pads last more than a season though...