......if i buy a vintage watch, I have no real knowledge of how it has been treated before or when it was last serviced. Also, especially with Patek, I like to make sure that the watch is exactly as it is meant to be...hence I will tend to get them serviced quite early in my ownership.
My 5070 was used a lot by me from new and actually needed a service. All the others that are vintage were sent for teh reasons above. I just wanted to be 100% sure. With my 5110G, for example, I sent to Patek because it had been serviced poorly by the previous owner...Patek pointed out the issues to me (hair in movement, small chip to city ring) and that allowed me to contact the dealer and get them to pay for the service...piece of mind. The linen dial vintage piece I had from our mutual friend in Paris......i have never seen a watch with that particular style of setup by Patek......so, to be sure, I let Geneva have it to verify it as fine.
The next service round for me will be in 10 years.