I don't do hoods - yet. I want to learn at some point, just not sure when.
Anyway, my wife used to run a kitchen in a local middle school. She tells me she would have thrown you out and reported you to the health department and told you stick your bill up your @%% if she even thought you were reusing plastic when cleaning her hoods. Her words - not mine. She's sitting right here. Sorry.
Even though they scrub everything down daily before they use any surface, it just adds an element of danger of contamination that no responsible chef or kitchen manager would knowingly risk. And I wouldn't want to be the contractor that put them in that position.
From your customers standpoint, wouldn't it look like you were ripping them off? They have to assume that the cost of the plastic is included in the cost of the job. Then you come back with used plastic and charge the same or more to clean the same setup. They aren't stupid, they know that new plastic comes from a roll, not out of a bag or other container. Why should they pay as much or more this time?
And what if you don't notice the roach eggs you picked up from the floor of the last job, and leave them at another job that never had a problem until they hired your company? That could be a reputation killer by itself.
I just think you are playing with fire by reusing plastic. I sincerely hope you never get burned, but it wouldn't surprise me. I guess my point is, it's not something I would do for the minimal savings. I'd rather bump my prices a few dollars to cover the cost of the plastic. You've been in business long enough to have built a good reputation in your area, so I doubt for a couple bucks you would lose any business. But you do what you feel comfortable with and what works for you. This is just my opinion. I don't mean to insult anyone, just trying to give another perspective.