The Restriction of Hazardous Substances Directive (RoHS) is not about preventing garbage in landfills, and frankly it's been 18 years and the sky is not falling.
Most current electronic devices are dumped much earlier than when they would fail due to the tin whiskers.
Many consumer electronic devices made 50 years ago are still usable without any problems caused by the aging of the soldering or of the semiconductor devices (but old electrolytic capacitors may have to be replaced). The electronic devices that are made now do not have any chances of such a long lifetime, with the exception of a few devices made for special requirements, e.g. military/aerospace.
The consumer devices which survived infant mortality, because they were free of manufacturing defects, had a negligible aging rate after that.
Modern electronic devices have far fewer initial manufacturing defects, due to automated production, but all age much quicker, due to very small component sizes, lower safety factors, surface semiconductor devices (MOS transistors) instead of bulk semiconductor devices (bipolar transistors), lead-free soldering and other similar changes in technologies.
But they could be easily repaired.
Very true, however having full documentation would help nonetheless. My water heater electronic board cost over €250 to replace, although it contains less than €20 parts; a preprogrammed uC makes it impossible to replicate it. If it had public hardware and firmware documentation, someone could repurpose a similar but cheaper board or replicate the functions using a different rugged enough uC board, which would also likely bring down the retail price of the original spare part.
Of course nowadays something that simple could be a chip the size of a rice grain, power included. So that's something :)
Sounds like you should unplug it before you open it up.
Citation required
As others have pointed out in this thread, reducing landfill waste from electronics is a much more complex problem and just adding leaded solder will not solve it.
Hence why I quoted the program name.