Only the current and maybe one more yearly folders are synced to my laptops, saves a ton of space. (Investigate selective sync on Dropbox)
I do have a gigantic hard drive on my desktop at home that has everything so I have one local copy of everything.
I also use Arq to periodically upload an encrypted version of the Photos folder from this desktop up to One Drive, since I get 1 TB free with my Office 365 subscription. Just for an emergency backup.
Hope this helps.