The most expedient and efficient way to browse a file

Question

I have a file that contains over 3000 tab delimited entries. As of now the file is open at start time and the data is placed in a list of objects containing twelve data members, and then accessed multiple times during the execution of the program.
I always thought it was the best solution (even though the creation of that many objects take space), but isn't there a more productive way to go about it i.e. open the file each time it needs to be searched or is that process slower?
Developing environment: Visual Studio 2010, Windows Forms MonoTouch and Mono for Android, Web Service.
Thanx
Luke