when you talk about lowering your standards reading between the lines i think your saying whilst you want to spend 3hrs per unit they want you to spend 2hrs? (eg)
assuming its time constraints, my initial feeling would be that they buy your services and so can buy however little they want and it wouldent bother me from that point of view, its their responsibility to buy enough time off you to get the job done to the correct standard regarding health and hygeine.
Having said that i would do one thing to cover yourself, I would write down the tasks your company will provide within the time they are paying you for, that way your responsibilities are clear.you could possibly do say 3 options, a 2hr list, 2.5hr list and 3hr list and let them choose "which suits them best".
from then on your duties are clearly defined and your only resposibilities are to your "list".
I dont think you should think of it as lowering your standards, more that they are lowering the amount of cleaning duties they wish to purchase from you.
if i asked you to do my house once a week for a hour and you said to get it to your standard it needs 2 hours, i might say well i only want an hour thanks! are you going to refuse to work for me? Im not an idiot (no comments thx!) i know i wont get 2 hrs worth in 1hr but thats what i want from you,1hr. likewise if i want 2 hrs worth, i know how to get it!
steve
p.s
If you do have concerns of peoples health being at risk, a quick annonymous phone call to environmental health will do it. when they ask for your name they sometimes need reminding that the key to the annonymous tip off is actually to remain annonymous!