I have no warranty statement on my contracts. I never get asked.
I handle any call backs individually. And with in reason. I ussually don't have hardly any call backs.
Don't supply the lights, fans or smoke detectors. If you do supply lights mark them up to cover any call backs.
If the fan wobbles. Some fans wobble a little. Tell them the balancing kit that all fans come with is in the kitchen drawer. I've already tried and checked it and it is a fan defect. Say I'll be glad to replace it if you go get an other one, I'll put it up for $125.00.
They ussually live with it. With in reason of course. I am not going to leave a real bad wobble.
After you have been called back on one thing you learn not to do it that way again. That's why I don't back stab my outlets or switches. I know that's been a debate here on the forum.
Sometimes I will put the hall outlets on it's own circuit. Some of these vacumes they use now a days are 10 -12 amps. If it's a custom home find out where they might use an iorning board. You learn what will last and what won't.
Some times if you go back. You may fix some thing small. but then they will want some recessed lights added. Or decided to finish the bonous room. That makes for extra $$ and you stay in good with them.
Call backs are not a problem if all your work is near each other.
It's them far off ones that can be a PITA.