[hadlock]

I'm still using an ancient copy of Navionics on a 1st or 2nd gen iPad (that was gifted to me from my mother in law, because it wouldn't run any of her Instagram stuff) on my boat to get around San Francisco Bay. The depth near the shore changes by a foot or two from year to year but otherwise it's fine for charting a course from the marina to the float-up bar.

[ghaff]

Cases vary of course but a lot of apps will break at some point if they've been orphaned and there's an OS upgrade (or, as other comments note, an online service has been sunsetted).

I expect the majority of apps I downloaded on my 1G iPad would not work today on a current iPad if not upgraded but if there's no server component, they'll presumably continue to work on the original platform.