I used to tip him for individual favors, now I just give him a fixed amount every month and forget about it. Easier for me and better for him - he can plan on a little extra coming each month. The arrangement has been working fine for the past four years.Yes, they are examples of them doing you a favour, so you return it. The end of year gift thing I also get, to a certain extent. But some poster here say they tip their potero all the time. For what?
By the way, everyone I know tips the janitor, whether they like him or despise him. I'm lucky to like Agustin so much, so tipping is no hardship.