Should I archive processed photos in 8 or 16 bit tiffs?

I'm looking for advice on whether to use 8 or 16 bit tiffs in my 'master archive' of processed images. I won't edit these in the future, but I'd like sufficient quality to allow me to 'process' them using process recipes for upload to various sites, perhaps print, whatever. 

Obviously, I'll archive the original raws incase I need to reedit with new found tools and experience. I'm just looking to ensure the resultant edits can be useful in the future. 

Cheers!