Magento – magento url rewrite prevent -1 or -2

I have a category created which contains url key as – "sofa" and url generated is "sofa.html". URL rewrites system record generated as follows :

ID Path : category/5
Request path : sofa.html
Target Path : catalog/category/view/id/5

Now I want to run one of the custom module over that url(sofa.html) so I deleted system url rewrites and added custom url rewrites from the backend as follows :

ID path : alternate-sofa
Request path : sofa.html
Target path : alternate-sofa

So when I run sofa.html from the browser, I got the expected page from the custom module and it resolves the issue removing custom rewrites after reindexing, though after reindexing new system record added as follows :

ID path : category/5
Request path : sofa-1.html
Target path : catalog/category/view/id/5

Now, I am having issue as follows : On the page, I am listing out categories on left side which contains category url as "sofa-1.html" which is displaying my category layout instead of custom module. How to overcome this issue? I don't want to create sofa-1.html, sofa-2.html, onwards.

Edit :
I refereed http://jc-designs.net/blog/2012/09/magento-adding-cms-pages-to-the-main-navigation/ and http://www.magentocommerce.com/knowledge-base/entry/adding-page-links-in-the-navigation-bar but when I set 301(permenant), url changed from "sofa.html" to "alternate-sofa" which is not expected url in the browser.