Are you running the router at the top speed setting or are you running at a lower setting to optimize feed rates and spindle speeds? The CNC Sharks have limited feed rates so you are probably running the router too fast. Running your router at a speed too high for your feed rates will cause the bit to get hot and dull quicker. Using the proper feed and speed for the bit allows the bit to cut chips that carry away the heat so the bit stays cooler. Running the spindle too fast produces dust and will spin the bit against the wood (rubbing) that produces a lot of heat. Running the router at the slower speed will also help to protect the router bearings from heat and prolong the life of your router. You don't say what model you are using, I'm guessing it is a Bosch 1617evs.
That is what I am using on my Shark HD1 and I am running mine on setting 3 which is around 16500. It runs a lot quieter at this lower speed and also makes it easy to get proper feeds and speeds for your bits. It is still noisier than a spindle would be.
Here is a speed chart for the setting on the Bosch 1617evs
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