From another comment above:

> Our projects are closed source due to our clients owning the code, but I can offer anecdote. We have a client whose business operates on 2-3 very niche SaaS applications in the veterinary/animal medicine space. In a span of about 6 months, we completely ripped out 2 of those 3 and are working on replacing the 3rd one right now. We've done this with a single senior engineer working with the client between 20-40 hours per week with no major regressions. The business has been able to continue working as usual with no disruptions throughout this process.

> Obviously it's hard to measure this objectively, but I can't imagine having done this pre-AI with zero downtime and having replaced those SaaS applications in that timeframe.