what's your thoughts on a one-time fee for tech things?

I like one time fees. But, most software products that I have bought on one time fees, usually do not stick around. Have switched on a couple of WP related products from one time fees to annual/lifetime license. So grudgingly accept that I need to pay for a continued and professional service. Thankfully have lifetime licenses to several products.

One-time fee isn't sustainable if the product in question requires updates over time or attract support, which probably covers almost everything, haha

Depends on the product completely. If it's a SaaS, the 'service' part seems to make sense as a subscription. Stuff like Ulysees and DayOne just feels strange though, like they're grabbing at MRR too desperately.

It's not sustainable if the product requires support / updates. So basically anything except static assets. :)