Cbhungry's post gave me a fright too! But I think I'm ok as I get pulse and BP checked every month when I donate platelets. I'm sure any problem would have been referred to.
I've cycled all of my life (well since I could straddle a bike), and when I cycled in my 20's my RHR was 55, now at 42 (and cycling many more miles) it is 44!
I was really surprised but have a HR monitor and check it regularly now.
My wife has a RHR of 50 but she cycles a lot too, and living with me causes her no stress
I've been a vegetarian for 13 years, and off much dairy for the last year or so. Maybe those are factors too.