Combine External Style Sheets?

I have integrated a WordPress theme into my existing website and everything appears to be working reasonably well. My question is whether it would be wise to go ahead and combine my external style sheets into one external style sheet.

I currently have the external style sheet that I used when I initially built my site and I also have the external style sheet that came with the WordPress theme that I integrated.

For those with more experience, is it smart to go ahead and integrate the style sheets into one document to make future style updates easier and provide a more streamlined maintenance process or should I follow the old, ‘If it ain’t broke, don’t fix it” mentality and leave it alone?

Thanks for your advice.
Jason