[deanhills]

Yes you will save a few amount of money on the domain costs. But it will probably waste all your past SEO efforts on the original domains.

I suppose if your websites are making some reasonable profits after 5 years, it is better to renew the original domains accordingly.

I'm not very seriously minded with SEO - mostly hobby domains and websites.  So don't think it will be a problem for me.  If it were serious though, I'd probably keep it at Namecheap and not fiddle around with the status quo.  I only have a handful of those category domains.  The rest were mostly acquired as a hobby and for fun.