Would You Make Common Variables Public?

It just occurred to me that I use certain variables in several of my routines. Maybe you've done the same... something like:

Dim db as DAO.Database
Dim rst as DAO.recordset
Dim qdf as DAO.QueryDef

Now, if it's re-used in many routines, wouldn't it make more sense to make it a public variable, and set them to whatever you need it for a certain routine? Would it be more efficient than having to re-initializing and discarding it for every routine that used it? What problem would one expect from making them public?

Also, since it's very common to set db = CurrentDb, would it also make sense to set it publicly, and for cases where you aren't using CurrentDb, use a private variable just for that one?