Man, hard to say without knowing all the details of an operation, but I think I would start with a harder study of your 5-day cycle. I would designate areas for a daily swab-a-thon and some daily product sampling from your normal Monday through Friday, test them for the parameters of your program, and see if there is a trend in results from day 1 to day 5. I would want to do this for maybe 3 separate weeks. If you can extrapolate any rise from day 1 to day 5 would still be within your established parameters by day 10, I'd say it could be worth a 10-day test run.
I think you should loop in your sanitation and maintenance guys: will a 10-day run cause a buildup of materials that they can't get clean in a normal cleaning period? Does maintenance foresee increased workload from letting the equipment run for double the current length of time? You can review their logs for the past few months to see how often they overrun their allotted times for cleaning (delayed startups) or how often you're suffering from maintenance downtime.
I'll admit I've never run in a plant with such a long cycle, and I'd be concerned about having to hold 10 days worth of product if the final day of production found an issue that causes a hold. Or god forbid a recall happens on a product produced on day 10 and you can't justify keeping it contained to that day's production (i.e. an unknown micro issue on day 1 isn't found until day 10). Even 5 days straight on a line would be a long run where I've worked, but I know plants do it successfully. I'm also concerned where you're saying you see a lot of flour buildup in your current operation: letting product accumulate on floors for 5 days is already a bad look, and if it were to extend to 10 days... yikes.
You would have to assume that on day 10, there is still some material left on the line that is from day 1 without a sanitation occurring between the lines.
