Yes I've definitely always struggled to keep easy runs 'easy' but I think this off period (as well as the heart complications) have given me a valuable new perspective. I also think that 120-140 for me is more like 110-130 taking my personal physiology into account.
Continuing to enjoy the off period and some cold Swedish weather over Xmas. I'm keeping runs <110bpm and <1hr but have been dropping a fast 1k every now and then to rev the engine (often ~3:00/km and HR well up in the 170's).
Aim to start training properly towards the London Marathon in late Jan (I have a sub elite start again) once the final heart tests are complete. I'm managing to keep mileage around 50-70k and weight <78kg so hopefully I'll be able to spring back fast.
Hope you and the family are having a great new year period