If the computer has only 12 cores, using all of them does not deliver the shortest possible solve time. Use one less than every core. There is also diminishing returns, so the solve time might not be much longer at 8 cores than 11 cores.
The number of nodes and elements in the simulation has a significant impact on the solve time per iteration. You could use a coaser mesh and cut the number of nodes and elements in half by increasing the element size. The ideal mesh uses smaller elements where the result change rapidly, either in time or location and larger elements where the results change slowly in time or location.
The time it takes to solve a transient model is proportional to how many iterations it must make. That is determined by the convergence criterion you impose on the solution. If you give it a small convergence tolerance, it will need more iterations, if you provide a larger convergence tolerance it will do fewer iterations.
The step controls is a place where you might have used a smaller value for Max time step when the solver would have been happy with a larger value. That does not seem to apply to your situation.
Just because the first 3 seconds took 14 hours, doesn’t mean you can linearly extrapolate to estimate the solution time for 600 seconds because the rate of change exponentially decreases and when it does, the time steps will get much larger and it might only need a few more hours to finish.
Click on the Solution Information folder. In the Details window is the Solution Output. The default setting is Solver Output. That is all text, but sometimes you get a clue as to what criterion is limiting the size of the step. Change the setting to Time Increment. On this graph, you can see if the solver is bumping up against a Min or Max Time Step limit you imposed, or if it is choosing the best Time Step it has decided on.
You can control how much output you are getting by clicking on Analysis Settings and going to the Output Controls category. Do you need both Stress and Strain? If not, turn off the one you don’t need. Change Store Results At to Equally Spaced Points and type in 300, then you will only get results on a 2 second increment over the 600 second end time.
What version of ANSYS are you using? Year and R#.
If you can share your model, use File Save As to a new name. In workbench right click on Model and select Clear Generated Data. That will delete the mesh, then File Save. Next do File Archive to create a .wbpz file choosing No Results and put that file on a File Share site like Googe Drive or OneDrive.