All of these factors can and will happen over time as you serve families. I strongly recommend charging people by-the-job as it allows you to get faster while maintaining excellence and make more. However, it can hurt you when lifestyle changes and scope creep, creeps in. You will make less and hurt your business.
"I told you, Ken! You should charge by-the-hour like I do and you'll never have this problem." I agree with you. If you charge hourly, you will not lose money when you have to clean longer. However, you will NEVER gain money or incentive to clean faster!
My ISO Model has a strategy for 3 things pertaining to price: