5/6 days Camino
If you fly into Santiago, most of the flights seem to get in around midday. Your best bet is to get a bus from the airport direct to Lugo and change bus at the bus station for Sarria. The bus starts in Santiago, so there does not seem much point in going in to Santiago, only to come back to the airport again!!!
If you want to catch the bus directly to Saria, you have to go into Santiago which is about 15k's from the airport, and you will get into Sarria quite late in the day, which might mean it is a little difficult to get a bed in the refuge.
The airport - Lugo - Sarria route will take around 3 hrs max and the buses to Lugo seem to go from the Arrivals terminal front door about every 2 hours. Cost one way last year was around 12 euros if I remember correctly.
If you take it gently, 5 days is ample. We did Sarria to Santiago in 4 days walking, but the last day involved 33kms which was very hot, very dusty, very thirsty, and knackered at the end, but as I had a very nice bed in a 5 star hotel awaiting, one kept going!!!
Having done Sarria to Santiago in Oct05, I am going back to do the 800km version in September this year.
The only problem with the Camino is that it gets addictive!!!
Regards,
Covey