LimeWire is hashing your files so files can be identified by a more secure attribute than just name and size. It's used to eliminate corrupt files and fakes in the gnutella network. I know it takes several hours to index lots of mp3s, but LimeWire will not index your mp3 collection twice, - unless you move, edit or rename your mp3s. You should get used to hashing since all future versions will have it. It may even be possible.

Version 2.4 will probably not be able to download popular files from LimeWire (beginning with 2.6), BearShare (4.0.2+), Shareaza (1.5+) and all other clients that implement upload queueing, so I'd not hang on to 2.4.3 if I were you.