We've all been there, and some of us have built multiple SaaS businesses, and it's becoming very similar to writing code - you start saving the most commonly used snippets that you use in other projects to speed things up in future projects.
You face the same flows with SaaS, but you can't just easily save them as they could be complex sets of knobs such as how to do marketing, find the target audience, and when you do how to reach them. If you've done it before and it worked, why not do it again?
For me it's the on-boarding process, I spend ages designing the on-boarding processes for my apps, and they are all the same flow, mostly, just like everyone else - register -> validate email -> create account -> add subscription, etc...
Let me know yours in the poll.