This is an often asked question, and the way around it is to ask yourself this question, do you have extra help like a hired staff or are you doing it yourself? If you have hired help, on a full time pay, it would be as often as possible in the most efficient manner.
If you are managing it on your own, you must schedule time to do it, like for example, every Saturday morning from 8am-12 noon. This is to ensure that you make full use of the limited time that you have especially if you having a full time job during the weekday. This is what I am currently doing. I get messages from my tenants during the week but I only inform them that I will take a look during the weekend. I will only attempt to do something about it immediately only if it is urgent enough like if the house is on fire, or if there is water falling into the house like a waterfall, which actually did happen when there was a leak in the pipes on the roof in one of my houses. The water flowed down up till a point that one of the tenants literally placed a plastic bucket where the water filled up so much until it was too heavy and broke the wet roof. The water was dripping into the room directly from the roof, now this is a situation that needs immediate attention.
Also when you plan your maintenance, you can go to the hardware shop and buy your supplies before the planned day. One thing to remember is that you may want to drive by to take a look at the problem during the week to evaluate the problem and you will know what kind of supplies to purchase and whether the issue is something that you can fix and manage or whether you need professional help from a plumber, etc.