For trouts, graylings and all light tackle fishing:
Tippet rings any time. Tied on with an Uniknot.
For salmons and seatrouts: Loop to loop connection.
The tippet ring was becoming attention in the 70Ďs of the last century as ĄPitzenbauer Ringď (called after the man who invented it). It was invented for dryflyfishing for grayling in Bavaria, to save the (time intensive) self tied tapered leaders of those days. There was a scientific around self tied tippets...
I donít know if there were people using a tippet ring for salmons or steelheads earlier than this in the States. If so, excuse me. But in Europe it was becoming popular much later for the salmon fishing.
Maybe I am alone, but I still donít trust a 180 degree knot in a combination of Mono and metal for the heavy tackle and big fishes.
In many cases itís a must to connect a fly, with one differentiation: It will be renewed regularly.
But for a longtime solution in the heavy game with all the mechanical stress of Spey casting, hookups, bottom contacts and anything else?
For the heavy duty fishing, I continued to use a loop to loop connection for nearly 40 years now without any problems. And the migrating fish species donít care.
I donít want to say itís not doable. Many people do so meanwhile, also without any problems (at least not reported) and the highly appreciated Simon Gawesworth and many others recommend it. It has itís advantages for fishing two flies of course. And itís more elegant too compared to a loop to loop connection.
If doing so or in need for a tippet ring, I would renew the knot regularly.
The power distribution in 180 degree knots on metal is simply different to a loop to loop connection. My loops on Polyleaders are mostly as old as the Polyleaders they are tied on.
Maybe the knots on the tippet rings too?
As said, maybe I am alone with my doubts. Interesting to follow what people will report about their experiences.
Time is running... A little bit of work, a little bit married, fishing, hunting... What else?