They provide an upgrade guide which is pretty comprehensive.
Im not saying it’s simple, but it certainly wasn’t as bad as I imagined it would be.
Good luck getting through it!
With the help of rector, it should be an afternoon's work to upgrade.
Yes you do. You're just choosing to spend that time on other things rather than pay off some of the technical debt (that the framework introduced rather than you). Your decision to just live with the old version will prove to be a bad one in the long term: you'll find it frustrating, your skills will stagnate, new hires will find it frustrating (and will quit), eventually 5.2 will stop receiving patches so your security will be compromised, and you'll miss out on some of the shiny new features in the latest versions. This will get harder the longer you leave it.
It's worth investing the time to move with the framework even if the framework is a pain at times.
I don't have any employees yet =) And I do firmly believe launching a few more features is worth more than eliminating some tech debt.