Third time lucky?

The living room in our house, which we bought very late in the 1960s, has an alcove either side of the chimney breast, a common feature of houses built before and soon after World War II.  We decided that we would like a light on the wall in each alcove and my late father-in-law, an expert DIY man, fitted them for us.  They were switched on buy a pull cord so there was no need to run wiring through the walls to a single switch.  Not surprisingly, by the late 2000s those lights were looking a little dated - very 1970s - and She Who Must Be Obeyed suggested that we should replace them.  I was, in principal, in agreement, especially as the only way I could remove the shades was by inserting the index and middle fingers of one hand and turning the fixing ring with the tips of those fingers, not a particularly easy job.

After many hours of searching we eventually found fittings we both liked.  There was just one problem: the wall lights had no pull cord to switch them on and they had to be wired in to the normal flick switch.  I gave the matter considerable thought and hit upon the solution, which was to place switches where the old lights had been and carefully cut a short channel up the wall so that the lights fitted above the switches with the bottom of the light fittings resting on the tops of the switches.  It proved remarkably easy, and it was a piece of cake to fit the three-branch matching central light.

All went well until, about a year later, one of the lamps in the central fitting went out, came back on a few minutes later, then went out again.  I removed the bulb - which looked fine to me - and fitted a new one.  This performed in exactly the same way.  I swapped it with a bulb from another of the branches, only to find the the "new" replacement didn't come on while the replacement bulb that I had put in another branch performed perfectly.  I diagnosed a wiring fault in the light fitting.  Having taken the fitting down and dismatled it as far as I could, I realised that there was one junction that I could replace, but I was unable to get to the area where the lead reached the lamp holder and Murphy's Law said that was where the fault would be.  The answer was to exchange the whole fitting.

I took it back to the shop, the local branch of a national chain of DIY stores.  As I was unable to produce the receipt, they refused to replace the fitting - even though it was one that was exclusive to that chain so could not have been bought anywhere else but one of their stores.  I swallowed my chagrin and bought a new fitting.  (I later discovered that we had bougt it not just the previous year, but two years and a day before my attempted exchange.)

Within a month, the new fitting played up in exactly the same way.  Yesterday I was finally able to take it back and get a replacement.  How long, I wonder, will this last?  Or will it be third time lucky?