If you care about support, within 3 years you'll likely need to update dependencies as well which means a recompile. You might as well change your target at that time. Honestly the breaking changes have been pretty minimal lately and it's pretty trivial to upgrade.
.NET Framework is part of Windows. That means it is very stable and supported for a very long time. But it is also not possible to evolve it further. That is why the .NET team forked it to make .NET Core, which is cross platform and installs versions side by side. This is what evolved into .NET, most recently .NET 8.
That means "stable" as in "it is not going to change".
But from a developer perspective, binding redirects, brrrrrr.... Also, source-level framework debugging tends to break every so often. It is obvious their focus is on the new .NET.
We're on .NET 6 now, because it's LTS. But as of today, it has 1 more year of support (1)
.NET Framework 4.8 as an OS component, is actually supported for longer - no end date given (2).
Note that .NET Framework 4.6.2 is supported until Jan 12, 2027 - that's longer than .NET 6 and 7, and maybe 8
1) https://learn.microsoft.com/en-us/lifecycle/products/microso...
2) https://learn.microsoft.com/en-us/lifecycle/products/microso...