One thing I always loved about music as a creative outlet is you can spend a couple hours writing a song and if you like it you keep it, if you don't you scrap it and start a new one. I can't imagine enduring a 4.5 year process and being your own harshest critic along the way.

I am sure you experience some of this in long term product building. To me building a business is much different than building/designing a product.