I have had one of the more expensive Philips DECT phones (Onis VOX 300) for
the last couple of years now, and of the 4 handsets 3 are pretty much
useless now as you quite literally have to stand on the buttons to make them
work. The 4th unit one is only marginally better... To make a key work
requires 2-3 attempts of pressing it from different angles, and involves
considerable force.

Any idea what is going on here? Can I do something to fix it, or is this
simply the life expectancy of these phones? Is it worth speaking to the
manufacturer about it (out of warranty by now)?

I also seem to recall that the previous phone we had, a top of the range
Panasonic (DECT as well) developed a similar problem within 2-3 years which
resulted in buying the Philips.

BTW, we are pretty light users and the house is kept pretty warm (young
kids) - could that provide a clue?