I'll give an real world example:
When I first started as a tech support person for my current employer, our website was outsourced.
I would send content changes to the web company. If I requested something as simple as an email link change, they would bill it as 30 min. (And we had a support agreement with them)
Now, as the client, I hated this. I knew it didn't take anywhere near 30 min. Maybe 30 seconds.
But now as a freelance web designer:
Whats the fair trade if a client only wants support/updates on an hourly basis?
What if I have a client that only wants to pay hourly, but only requests changes 3-4 times a year, that only take 15min each? Part of me thinks I should charge this client a 1 hr minimum each time. Not just for the 15 min of labor, but the response time, putting aside other clients to, and a premium for not being a regular client with a support plan.