I would like to post a situation update, for those interested.

Having played around with the monitor's settings a bit, I can report the following:

Lowering gamma from 2.2 to 2.0 improves brightness quite a bit. I am now able to reduce backlight brightness to 65% (it was 85%) and the image looks quite bright in a lit room.

In addition, shifting the white point from 6.500K to 7.000K improves contrast (text becomes more readable & crisp).

So now the situation is much improved and the settings are as follows:

Brightness: 65%
Contrast: 55%
White Point: 7.00K
Gamma: 2.0

At this point, I would not assume the risk to opt for a lamp replacement, the risk/ reward ratio is unreasonably high. Unless the situation worsens the monitor is quite usable as is and the image quality is very satisfying...