As long as the 4 packs contain the same number of cells you can parallel any number of packs together. Using 4 would indeed give you a 6000 mah 11.1 volt pack and can be treated as such when charging and using. It can and should be left together if used together.

All the + will be hooked together and all the - will be together. Same for the balance taps if you want them to stay equally balanced between packs as well. I can see it getting very messy with 4 packs and having a lot of cost/labor/complexity compared to one pack.