^ squeezing the bar hard helps alleviate elbow pain.
I've done pull-ups everyday for years ... The trick (as stated above) is NEVER go to failure on your sets. For instance, I might do 4-6 sets of 8 everyday, or 3 sets of 12, or 2 sets of 15 .... Look at it as just increased volume. I wouldn't do multiple max sets trying to hit 50 reps as fast as possible. Better to break it up into 5 sets of 10, 7 sets of 7, or something like that
The neutral grip is also a great idea - I've found it much easier on the shoulders
I'd also recommend never trying this with weighted pull ups - surefire road to elbow issues/ tendinitis
FWIW I'm not 50, but I am 45