How long does a refrigerator stay cold?

First use: How quickly does a refrigerator get cold?

I'm trying to assess where the problem with my refrigerator is. I haven't used it properly for a while, recently defrosted it and now it seems to me that I have a problem with the cooling performance. I'll describe it as best I can.

Model: Premiere AK260i Fridge & Freezer Combi Age: 9 years

I defrosted it on December 26th. and reconnected about 48 hours ago.

Maybe I'm just imagining it, but the fridge doesn't seem to get really cold, just cool. Condensation water easily collects on the back wall and it also feels cool, just like the whole box, but not really cold.

The freezer part of the device freezes water as normal, I tested it. It seemed to me that it took a little long, but that was a maximum of 24 hours after defrosting, maybe that's normal then?

The box is currently buzzing happily, so you can hear it working.

So much for the description of the situation.

Since the freezer compartment gets cold enough, it can hardly be the refrigerator itself, right? Can they get weaker? I only ever heard that they fail completely. I suspect one of two things: Either I'm impatient or overestimate the normal cooling capacity, or the thermostat is crazy. But would the box run then? Actually, it should be over by then.

It would be nice if someone who knows about refrigerators could give me a nudge in the right direction, thank you!