The location, size and shape of the holes/punctures tell a lot, without better description of the holes I don't see being of much help. Rubber does degrade with time and can start to crack with it's being bent and stressed (like sitting of flat tires). Tubes leak air naturally, just at a rate that most won't call "being flat" but still enough to have the suggestion of frequent pressure checks making good sense.

Punctures along the tube's sides can suggest a tire sidewall issue or riding with too little air pressure (pinch flats). But could have other less common causes. I can't see the rim strip having any influence of this type of flat.

Punctures near the valve might be simple poke throughs from some object or indicate a seating/fitting issue between the tube/tire and rim. But the base of the valve is a common spot where the tube won't always fit snug down against the rim's interior and can cause the tube to expand (like a balloon) into the gap. This spot will have a wall thickness, of the tube, that is now thinner and can easily burst (like an aneurism). When mounting the tire seating the valve down against the tire's beads and/or the rim helps limit this.

There are many times where novices can't find the causes of their problems but if an experienced person were to have a look the solution would be had fairly quickly. Is there a friendly bike shop near you? Andy.