The plan from
@stratophile gets my thumbs up - not just for the distances but for stopping in some of the best places (Tabara, Albergueria, etc.). Here are a few tweaks that reflect my preferences. They might not suit everyone:
Day 5 - If you can handle another 6km, you could enjoy dinner at Me Gusta Comer in Rionegro rather than staying in Villar de Farfón. (For me, the choice is easy).
Day 17 - Check the latest reports about the albergue at Laxe. Apparently its due for some improvements (a huge budget has been allocated, so it should be transformed) . As an alternative, there's a super albergue with the friendliest owner in central Lalin. (Lalin is a 4km detour off the Sanabres - Next day you can follow the Camino Invierno, which merges with the Sanabres at Laxe).
Day 18 - Rather than staying at a hotel in Bandeira, I recommend continuing to Dornelas to enjoy the hospitality of the Italian couple who run the albergue there.
Day 19 - Outeiro is great if you like to be surrounded by nature (buy food in Ponte Ulla). If you prefer to dine out, stop in Ponte Ulla. If have energy in your legs, press on to Deseiro Sergude for a super new albergue with a bar-pulpeira next door and a sprint finish to Santiago next day.