I didn't know they could get too old! I'll have to pay attention to see if anyone else answers this for you!

Yeah I was just wondering if maybe after they get to be really old they might lose their vigor and vitality, regardless of the other factors. Overall health maybe start to deteriorate naturally because of old age.

A representative of a Group in Abbotsford, BC, is seeking to preserve a healthy grove of rhododendrons in the area that are 60-80 years old from a development proposal. I was asked "How long do rhododendrons live?" Obviously, many factors are involved, but the Group feels that if a few hundred years are common, their case would be strengthened. Would it help if the species or hybrid type were known?

Okay thanks for that link albert_135. Apparently then they can sometimes age up to a few hundred years old. Pretty sure mine aren't even 40 yet. That means I'll have deteriorated from old age well before my rhodies do.