I've recently started my exercise regime and have installed a chin up bar at home. At first I was hitting 4 sets of 10 then the total number rose to 80, 100, 120 etc over the months, today I've hit 200 within 2 hours, I was aiming below 1 1/2 hour but it's kinda hard as my forearm starts to cramp thus have to stretch my resting time.

I don't do this often, maybe once a week while rest of the days I'm training on other parts of the body. Is it alright to hit this amount or a waste of time? I'm not adding more weights because I'm afraid the excess weight will bring down the bar.

I'm standing at 1.72 and weigh 69 KG.

Wanna build my lats and back muscle, also to test my limit (Pull ups happened to be my favourite exercise). It's been donkey years since I last hit the gym, now wanna start training back. If it's too excessive and won't help effectively in building back muscle then I will do some adjustment to it. As mentioned I don't wanna add weight to my body because the bar may not be able to take it. 

From now will tweak my pull ups exercise, gonna load weight plates into backpack. Since 2 hours of pull ups is time consuming and also ineffective, I'll need to up the scale as suggested. Thanks!