It depends on the site and the use case, but I'd have thought that if you do, say, 10 minutes of interactions with a complex application, every few days, a chun

It depends on the site and the use case, but I'd have thought that if you do, say, 10 minutes of interactions with a complex application, every few days, a chunked and cached SPA payload, with fairly light fetch requests for json after the initial load, would probably result in less transfer overall than a standard website. And again, leaving marketing / advertising / analytics scripts out of the picture, the JS in both cases will be a tiny part of the transfer when compared to images.