Storage isn't the only thing that determines how well ProSeries will open. 

Make sure your computer also meets minimum requirements for PS listed here: https://proconnect.intuit.com/support/en-us/help-article/product-system-requirements/system-requirem...

In my experience, i7 Processor, 16gb RAM and a solid state drive has given the best results. 

It still takes less than a minute to open up the first time, but less than 20 seconds when you open & close frequently.