Ed, you're on the money. We self-manage four holiday lets, and they are a lot of work. As you said, along with the cleaning is the linen and other inventory stuff - you need to check everything (to make sure there's a full complement of teaspoons, dessert spoons, etc through to saucepans), that they don't need to be washed, that they're not damaged..... We also wash everything in between our lets - doona/duvet inserts, pillows, etc. This does all take a while! Then you need to factor in things like cleaning the oven, getting the carpets cleaned, etc etc etc. This is all assuming there aren't any actual repairs that need to be done, or anything like painting of rooms etc.
That said, our approach is successful in terms of money and also personal satisfaction with how we do things. We only have about six to eight weeks' vacancy per property per year, and we require a minimum lease of eight weeks. We couldn't do it if it were any shorter, it would just be unmanageable. We both have full time day jobs, so we manage the properties around that (and we do everything ourselves).
There is definitely a niche in the market for self-contained holiday lets in Perth, particularly in areas close to the CBD and/or beach. I would love to pick up another property soon but the other half is happy to wait a while, for some unknown reason!