If you feel your Lightroom Catalog is too bloated and slowing down as you import more and more images, you might read through Jeffrey Friedl's blog page on the topic. Jeffrey is quite knowledgeable on Lightroom — he develops useful plugins for Lightroom. 

The technique is simple and he details the steps very clearly. I've tested it on a catalog and it did reduce the catalog size.

However, please read the article twice and carefully. These steps delete the editing history that accumulates when you work on images, thus trimming down the overall size of the catalog.

You first need to ask yourself:  if I were to revisit the images at a later date, would I want or need to go through the editing history of the images in the catalog?

If you do decide to follow the steps, and have read through them twice, be sure to back up your Lightroom Catalog and store it on another drive or separate location before your start.

You do keep at least one back up of your catalog or catalogs, right?

 Remember, the Lightroom Catalog is a database that stores information. The Lightroom Catalog does not store your image files, which should also be backed up to another a separate drive, a different one than where you keep the main folder of images.

Here is a link to the article:

http://regex.info/blog/2014-06-26/2434