I don't usually stay at a place more than 3 or 4 hours anyways, so it's just a midway refill point for me. I usually work the rest of the day at home, or switch to a new place if I want to stay out.
Also, the amount to spend can scale with your budget; it seems more important to just to get up and buy something, just so you don't appear completely cut off from the rest of the world.
I normally get espresso drinks, but sometimes I'll get a normal drip coffee, which usually has a cheaper refill ($3 for the first, and $1 for a refill), and I'll tip on each refill.
Also, the amount to spend can scale with your budget; it seems more important to just to get up and buy something, just so you don't appear completely cut off from the rest of the world.
I normally get espresso drinks, but sometimes I'll get a normal drip coffee, which usually has a cheaper refill ($3 for the first, and $1 for a refill), and I'll tip on each refill.