The threshold has nothing to do with how many items can be in a library. It has to do with the performance of the views. So, keep the threshold low, and configure views to only show a small number of items at a time, like items added today (and index the fields you're using to filter the views).
If you increase the view threshold anyway, you're going to have significant performance problems on your site.
As @Mike2500 points out, changing the threshold is not advisable but there are other alternatives to handling this, such as folder organization, key fields and so forth. This "Training Course" from Microsoft is one of the best resources that I've run across on how to handle the Large List issue and should provide you with a few options that might work in your situation as well as an understanding of the underlying issue itself