There's no need at all to lube most of the stuff monthy. A good grade of boat trailer water resistant wheel bearing grease will easily last a year or even three if you don't ride often or in harsh wet conditions. On the other hand the chain and sprockets will benifit from a clean and re-oil whenever the chain looks black or feels gritty. This can equate to a chain clean and lube every 1/2 dozen rides if you see a lot of rain during that 3 days of back and forth.
Generally if there's ball bearings involved like in the hubs or steering head then clean and grease once every couple of years or once a year if you commute heavily in bad weather. Also when you wash the bike set the spray nozzle to a force that you would use on a fairly delicate garden plant. No strong blasts or you'll find it pushes water in past the seals very easily.
Brake and shifter cables can benifit from a thin wipe of a light oil. No grease here as it is too sticky. However the shifter pods or grip shift units generally need some grease inside them to work smoothly rather than oil.
For oil you can go Triflo like so many here do or you can buy a bottle of 10-30 motor oil and use the same bottle for the rest of your life provided it's only for bicycles. That and the little tub of water resistant boat trailer bearing grease and you're all set.