Compression/Archive app question

[PreOmegaZero]

Looking for a compression app that compresses well (will be compressing over 10GB of PSD's), BUT allows me to ADD new files to it WITHOUT re-compressing the entire archive. At the moment I'm using WinRAR with RAR compression, but if I add/update to an archive with say...1 file, it will re-process the entire archive which can take an hour or more. I would just do a fast compression, but with all these files (over 1500) it still takes forever, so I might as well get the best compression if I'm going to wait so long.
Any suggestions?