Developers spend about 17 hours a week on maintenance and bad code, per Stripe's developer survey. That's 42% of the week.
If your roadmap keeps slipping, look at what your team spends its week keeping alive before you hire more people.
Now count.
Two: fix the worst one this quarter.
Three or more: price the rebuild before budget season. You're already paying for the old platform, spread across payroll, overtime and lost orders.
"The site feels slow" usually isn't one. Rebuild the front end on top of 30 apps and you've just moved the weight somewhere more expensive.
Remove before you rebuild. What's the oldest app still running on your store?