One easy way to reuse symbols is to save the lyr files for each layer, and then import the symbology from a saved layer file (from the layer's property dialog box).
A second method to reuse the symbols by some creative renaming of the mdb and mup. For instance let's say you have:
MyOriginalModel.mup
MyOriginalModel.mdb
MyNewModel.mdb
rename MyOriginalModel.mdb to MyOriginalModel_renamed.mdb
rename MyNewModel.mdb to MyOriginalModel.mdb and the old MUP will point to the new data
I believe a third method is to force Mike Urban to prompt you for the database:
[list type=decimal]
[li]rename the current mdb that goes along with an mup file[/li]
[li]open Mike Urban and load the mup file[/li]
[li]when Mike Urban can't find the old mdb database, it'll prompt you for the location of the mdb database, which you can point to the file you want to reuse symbols on[/li]
[/list]