Do you think I should spend $2600 and add exhaust brake?

Pacbrake looks to be about $1500 +/-. Install isn't too bad. I do recommend the shifter mounted on/off switch if your truck is a manual transmission. Also includes emergency onboard air. I have 118k miles on my 2006. Still have over 50% factory brake pad life. This is towing heavy through mountains. I typically crest a hill about 5mph under the speed limit. Then ride the exhaust brake all the way down. I rarely use vehicle service brakes. This leaves brake pads cold for maximum capability in case of emergency.