I think that the OP might have meant that it’s good practice to store local copies of research materials in an app like DT when you can, because we can’t rely on them still being available on tap in the future. Rather than DT itself disappearing. The post was advocating for a LOCKSS approach with a significant personal research management component? I may be wrong :-).
I speak as someone who isn’t yet super old but has already seen paper journals go the way of the dodo (paperbound journal issues that used to be hardbound into a year collection by your local academic library; then stacked onto the shelves for browsing; then moved off those shelves to offsite ‘research stores’; and then pulped because no one calls them up anymore and ‘everything is online these days’…).