Some food for thought...
In times of abundance, I've had great luck in fall SH fisheries in WA / ID / OR / BC using float/float or float/intermediate setups as long as there wasn't ice in the river.
I've also raised fish to topwaters in water temps as low as 41° 'Merican.
I also have the good fortune of knowing crazy folks who fish float/float year-round and do well.
I've also had some positively ridiculous days in late fall fishing heavy flies on full floater setups...
So the crux of the problem becomes - what do YOU want out of it?
Do you want to catch a fish by any means possible? Pull a plug or drift some bait.
Do you wanna catch a fish on a spraypole? Fish a skagit head and 11' of T10 with a 2.5" black leech with some blue flash. You're welcome.
Do you wanna admire the sexy loops of a scandi setup all year long? Fish a float/intermediate and your favorite fly and get it done, fisha.
Do you wanna be like the last LSpencer acolyte and fish nothing but blunted muddlers when you actually fish?
The path is yours, mang. Have fun however you roll.