The payback for doing "favors" for your clients is big, in my opinion. I love helping people and giving advice; yes, I suppose there are limits to how many times I will drive to a client's house because they want me to check on purchases they've made on their own for staging, or colors they picked out to paint with, or checking on landscaping changes they've done following my advice. But so far I honestly haven't reached those limits because no one is taking advantage of me; they seem to be reasonable people who will either ASK me if they're taking advantage of my time, and if so, to please charge them for it (how great is that? But I don't) or they just ask for one extra favor, not many.
I'm sure agents do LOTS of extra favors for their clients, but in the end, isn't that what not only makes us feel good, but gets us great word-of-mouth referrals?