One night stay with a single restaurant would be in the 8 hour range for sure...but I don't see as many of those as I used to. I am seeing a trend to move to dining-intensive assignments where you have almost no time on property to do any work. In the past I used to do two night stays where you would get a single room service meal and a breakfast one morning. I could always knock those out with one day of work when I got back home.
The thing is, they have been changing up the standards in recent years, and adding more sections to the reports. You cannot see the requirements in advance of being assigned a shop, but I usually have some expectation based on prior shops for the same client of what will be required.
My most recent shop decimated all of my expectations for reporting time. I had done hotels for the client in the past, but they had changed so many things, it was like a brand new client. Constant eating. Numerous complaints. Multiple bars. Retail section. Pool section. Gym section. STEAM ROOM section. Honestly! There were separate sections for valet from bellman, but it was the same employee doing all of it, so I had to come up with a narrative that separated it out. The dining components had new sections with standards that have not been present for other hotels or restaurants in the past, so that took extra time to format. The bars had bar + lounge requirements, with even more food. There were multiple calls required outside of the reservation call, and all of this was for a hotel outside of the US where the staff were not native English speakers, which made collecting names difficult, and transcribing the phone calls even more so. The requirements were so absurd that it made it obvious I was the shopper, and that brought even more interactions with management constantly checking on me.
In the end, I had to put in three full days of work to get the report submitted. I have learned and will pass on anything moving forward that requires that much work. It was not worth it.
My recommendation is to apply and then don't feel bad about declining a shop once you see the requirements. If they are not going to disclose them up front, then they need to be understanding about shoppers cancelling after the shops have ben assigned. A more recent thing I have noticed is there being no mention of valet parking being required in the description, but then being required to park a car at the hotel, so it means extra car rental fees if you are flying in.