If I get a card I have I always send a return. But I have the same old boxes of cards I got in1984 and have to write in grid, CQ and zone. Just a generic card. When I got back more active I discovered eQSL and I put every contact from the station on eQSL waiting for them if they desire or need and absolutely free of charge (ham radio without all the BS of $$$ for everything??). As a courtesy to others I put every contact on LoTW and keep QRZ updated as it should be. If any on a wants or needs a conformation is is there waiting for them as is the decent thing to do... With the electronic age it should be a snap? But I am just damn lucky if I get a conformation from 25 contacts.
Here are TWO QSL cards that I maintain.. the K4L will be updating to wB4SA when the new shack goes online at camp.