iPads are Apple's best products. They almost never get old. They work for years.
I agree. The iPad is a good investment as a product. Whatever you end up spending on them you get that back and much more. I'm still using my 4+ year old iPad Air 2 and love it. It works perfectly and I have no issues with it. In fact, it feels as snappy as ever.
I'd like to upgrade to the one of these new iPads Pro simply because of the new screen, the pencil, USB-C, and the seemingly amazing internals. But I don't feel I need to. Usually 4+ years in with a laptop I feel I need to upgrade.