I also think this deserves further qualification. I agree that in general we should be telling users: yes, if you want to pin your work to a specific release of Astropy for a long period of time you should use an LTS.  But I think that even for non-LTS or even expired LTS releases there should be some allowances for critical bug fixes--primarily security-related (which are likely to be rare but not inconceivable) and things like "The upgrade costs are too high/risky but if this bug isn't fixed the spacecraft will crash" kind of issues.  This would be exceptionally rare I think, but I think this should be stated explicitly (although the criteria for what qualifies may be loose--I would take it on a case by case basis).