Autocomplete vs. Drop-down

I’m working on the project where I have form with 4 select boxes. The problem is that selects are backed by the db tables and can vary in size (grow or shrink). If the select grows back beyond 20-30 entries it becomes pretty much unusable and that’s when I want it to become an autocomplete field.
I’m using QuickSelect as autocomplete and was thinking to extend it to support drop-down functionality.
And then it struck me – there’s absolutely no need! All I need to do is at the run time determine how many entries are going into the control and then initialize the input box to ether drop-down or autocomplete which could be separate plug-ins. On Monday I’ll add some code examples on how to do it but I think that will work just fine