My last Camino was 373 days total, though that was in four stages -- my fourth and final stage was about 8½ months though.
I am very slow now, which is the only reason why it took so long, though my route was exceptionally lengthy (~5,000 K) and included Santiago > SJPP > Lourdes (I had wanted to walk home, but I reached SJPP on the 1st January last year, and the winter conditions prevented me going further than Lourdes ; if I had reached SJPP a month earlier, it would have been fine and I'd have walked another ~800K to home).
Someone healthy should do about 25-30 K/day average on any very long Camino (most people would quite naturally start to get faster), and 365 * 25 = over 9,000 K ; even just 365 * 20 is over 7,000 K, and that's significantly longer than Jerusalem to Santiago. Personally, at my old very fast speeds, a year's walking would have been about 13,000 to 15,000 K, and honestly about 10,000K would be a reasonable expectation for a full year's hiking ...
So really, the only way for a normal, healthy pilgrim to manage 10,000 K on a single Camino one way to Santiago / Fisterra would be do something like start from home somewhere in North America or wherever, preferably the midwest or further West, walk to a port on the East Coast, get passage to European port very distant from Santiago, then walk on from there. Unless you're walking from home in Asia or something.
In practice (withstanding exceptions like my own), the only pilgrims (and others) who are on the Camino Ways for such lengthy periods of time either living on the Camino full time or, more rarely, are walking Camino after Camino after Camino for non-hobo reasons, though the few that I've met in the latter case most often spend about 6 to 9 months doing that, then winter at home. You do come across the occasional semi-pilgrim oddball, such as one fellow I met on my first day out from home in January 2019 who was walking to Nepal from IIRC Valencia via Santiago and Rome.
The Camino in Winter is OK on major routes like the Francès or the Le Puy routes, and should be OK on the Portuguese, in other cases it would be better in Winter to be in places like Mediterranean France or southern Spain or Portugal and so on.
On the more inland routes that aren't the Francès or the Le Puy, as well as those in Mediterranean France or southern Spain or Portugal, there is very little pilgrim accommodation in Winter (unless you're wealthy enough), and if you need to sleep out and whatever (which will occasionally be necessary, finances regardless), best be where the Winters are warmer.
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Honestly, unless you have some meaning and purpose for it, or like me some disability slowing you down, there are not many good reasons for spending a year on the Camino. Some pilgrims do take about a year to walk Santiago > Jerusalem or the other way, but in those cases they typically take not rest days, but rest months.
I guess you could do something like a Rome > Cádiz > Faro > Lisbon > Fátima > Santiago > SJPP/Somport > Lourdes > Rome which could take a healthy walker about 9 to 12 months ? Or something like Canterbury > Rome > etc. or another similarly circuitous route ?
I guess that a route comprising every major Christian foot pilgrim sanctuary destination in Western Europe -- so Walsingham, Canterbury, Chartres, Paris, Vézelay, Le Puy, "Arles" (i.e. actually Saint-Gilles), Rome, Lourdes, Manresa, Montserrat, Fátima, Santiago -- plus a Mediteranean route such as Rome > Cádiz for wintering purposes might add up to a year ?
But it really has to be something with both purpose and meaning beyond just "spend a year on the Camino", less it turn into an aimless wandering.
Like a wayfaring stranger, wandering roaming pilgrim, not sure if the Spanish authorities would appreciate that though or allow it, I think you have to leave the area after a certain amount of months, and then re enter, got to double check that though
