If I don't claim my Post/Comment rewards, is there a time limit to claim them? Will the rewards ever dissapear or I'll be able to claim them even 1 year later?

Till now there is no any limit to claim your post and comment rewards in steemit.if you don't claim your rewards then it would be your loss because if you do so then the price of the steemit increase and decreases going and you will too much loss due to this .

If you don't claim then there will no reputation score increase and also you cannot get good amount of upvote and you can able to earn more money.if you don't claim the reward you cannot convert your earning to sbd and also your balance remain constant.

The rewards you get in steemit will not be disappear even if is 1 year or more because there you see a reward claim option and you can redeem the claim bonus anytime when you are free so don't worry to claim post and comment reward but if you redeem it will be beneficial to you only.