Having a large number of entries in Smart List

I'm using EPMSW, Fusion Edition. I would like to know what kind of performance issue I could expect from having a field on a data form whose data type is SmartList, that has over 16000 entries in it, from the users' standpoint. It's a field for a code (16 digits/characters long), and if I didn't use SmartList, users would have to enter something like "CC18100010001001" and I don't want them to. As they type the code, the list narrows down the entries, so that is nice. Some people have said that both IE and FireFox don't handle a large number of entries in SmartList very well, but they didn't say exactly what they don't handle well. If it takes long to load (Application->Import and Export) or fetch the list (Application->Manage->Smart Lists), it's okay because users don't see