Printer toner doesn't adhere well to the paper anymore

We've had the Samsung SL-M2825DW for about 2 years now, and printed a total of 5345 pages (according to the configuration report).

Recently, I've noticed that the toner doesn't always adhere well to the paper after printing. At first it seemed to only happen after printing dozens of pages, but now it seems to happen even from a cold start.

As you can see, I can easily rub it off from certain parts of the page. However, other parts of the page seem to be fine.

From what I've read so far, it is most likely due to some problem with the fuser unit (which uses high temperatures to fuse the toner to the paper). I've tried cleaning the rollers in the toner, but that didn't seem to help much - I suspect that any residual toner I see on the rollers is just left over from not adhering to the paper.

Is the fuser just reaching the end of its life? The estimates I've seen for fuser life are typically in the 100K page range. So, I am surprised that I've only gotten about 5K pages, even with this lowest-end consumer printer.

Other possibilities I've considered are:

• Paper type. We've been using the same kind of paper since we got the printer, the Astrobright series from Neenah (weight 11.8 M, basis 24/60). So, unless the paper has significantly changed formulation, I'd be surprised by this. I even tried adjusting the paper thickness setting on the printer to maximum thickness, in hopes that it would print more slowly or at a higher temperature to help the toner adhere;
• Toner quality. We've been using an offbrand toner cartridge, but again we didn't seem to have a problem with this toner a year ago.
• Eco mode. We print using "eco mode", which is supposed to use less toner. Again, I don't think this caused any problem a year ago.

Is this typical for low-end consumer printers? Would a more expensive printer have a longer-lasting fuser unit?