I installed the 30 ml oiler (Sport version), and the manufacturer claims that 30 ml will last 900 miles. So you're talking about over 7K miles for the 250 ml bottle. And the oil is cheap to purchase. Here's the problem with "regular maintenance": spray lube (either oil or wax) is tacky and attracts dirt, eventually forming a gritty gum that grinds up your o-rings. Once the o-rings begin to fail, your chain will deteriorate quickly. The blue oil that comes with the Scottoiler is thin and not tacky. Only one drop is applied for every minute of riding. Sling is minimal, and the chain has the happy appearance of a moist dog's nose at all times. One exception is after a rain storm, when the oil will get stripped off. (Then you can drizzle a bit of the blue oil on the chain after the water dries off and you're back in business with a chain and sprockets in brand-new condition.)
With the Scottoiler properly installed and calibrated, you should never need to clean your chain again, and the lubing is automatic and perpetual. If I sound like an advertisement, it's because I think this thing is a brilliant invention. One in six bikes in the UK has it installed (the company being based in Scotland).
The oil is applied by a plastic nib that lightly touches the rear sprocket at the 6 o'clock position, pointed downward. The oil is slung onto the inner plate of the chain and ends up lubricating the rollers and o-rings by capillary action. Since dirt particles don't stick to the chain, they get slung off. The chain and sprockets thus stays shiny and free of contamination.
A BMW rider used the Scottoiler in the Paris to Dakar race, through the African desert, and it worked.
The cost is $140, and it took me a couple of hours to install it. I used the cylinder 2 plugged vacuum port (not wanting to mess with the MAP sensor vacuum line).