Hi Matthew, changing the color or strength of a light starts the render over, but that was also the case in 2.79.
Clicking a node only re-starts the render since 2.8.
Stupid question, but are your .blend files on a SSD or still on a HDD?
The thing is, SSD’s have a weak point: writing. As .blend files are constantly changing (‘Save’. With every ‘DO’ there has to be written a new ‘UNDO’ (bad formulation, but…)), there is a lot of writing to be done and that will reduce the lifetime of a SSD. (Don’t know if it will slow down first or just stop working…)
Also please don’t tell me you defragment your SSD.
You might know all this already, but I’m just looking at possibilities here…
